Document:

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                                                                     EXHIBIT 4.2

                                  NANOSYS, INC.

             SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT

                                 APRIL 10, 2003
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                                TABLE OF CONTENTS

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1.  Information and Other Rights........................................................................................      1

    1.1       Financial Statements......................................................................................      1
    1.2       Material Changes and Litigation...........................................................................      2
    1.3       Access....................................................................................................      3
    1.4       Proprietary Information Agreements........................................................................      3
    1.5       Stock Vesting.............................................................................................      3
    1.6       Reserved Shares...........................................................................................      3
    1.7       Board Meetings............................................................................................      3
    1.8       Qualified Small Business Stock............................................................................      4
    1.9       Termination of Covenants..................................................................................      4

2.  Registration Rights.................................................................................................      4

    2.1       Certain Definitions.......................................................................................      4
    2.2       Demand Registration.......................................................................................      5
    2.3       Piggyback Registration....................................................................................      7
    2.4       Registration on Form S-3..................................................................................      8
    2.5       Expenses of Registration..................................................................................      9
    2.6       Registration Procedures...................................................................................      9
    2.7       Delay of Registration.....................................................................................     10
    2.8       Indemnification...........................................................................................     10
    2.9       Information by Holder.....................................................................................     12
    2.10      Rule 144 Reporting........................................................................................     13
    2.11      Standoff Agreement........................................................................................     13
    2.12      Limitation on Subsequent Registration Rights..............................................................     14
    2.13      Mergers, etc..............................................................................................     14
    2.14      Termination of Registration Rights........................................................................     14

3.  Preemptive Rights...................................................................................................     14

    3.1       General...................................................................................................     14
    3.2       Right of First Offer......................................................................................     15
    3.3       Expiration of Right of First Offer........................................................................     16

4.  Miscellaneous.......................................................................................................     16

    4.1       Transfer of Rights........................................................................................     16
    4.2       Waivers and Amendments....................................................................................     16
    4.3       Notices...................................................................................................     16
    4.4       Descriptive Headings......................................................................................     17
    4.5       Governing Law.............................................................................................     17
    4.6       Counterparts..............................................................................................     17
    4.7       Expenses..................................................................................................     17
    4.8       Successors and Assigns....................................................................................     17
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                                TABLE OF CONTENTS
                                  (CONTINUED)

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    4.9       Entire Agreement..........................................................................................     17
    4.10      Separability; Severability................................................................................     17
    4.11      Stock Splits..............................................................................................     17
    4.12      Aggregation of Stock......................................................................................     18
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                                  NANOSYS, INC.

             SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT

         This Second Amended and Restated Investors' Rights Agreement (this
"Agreement") is made as of April 10, 2003, among (i) Nanosys, Inc., a Delaware
corporation (the "Company"), and (ii) the persons and entities listed on Exhibit
A (collectively, the "Investors", and each individually an "Investor").

         WHEREAS, certain Investors (the "Prior Investors") own (i) outstanding
shares of the Company's Series A Preferred Stock, $0.001 par value per share
("Series A Preferred Stock"); and/or (ii) outstanding shares of the Company's
Series B Preferred Stock, $0.001 per value per share ("Series B Preferred
Stock," along with the Series A Preferred Stock, collectively, the "Prior
Preferred");

         WHEREAS, the Company and the Prior Investors are parties to an Amended
and Restated Investors' Rights Agreement, dated as of January 18, 2002 (the
"Original Agreement");

         WHEREAS, certain Investors desire to purchase shares of the Company's
Series C Preferred Stock, $0.001 par value per share ("Series C Preferred
Stock"; and together with the Prior Preferred, the "Preferred Stock") pursuant
to a Series C Preferred Stock Purchase Agreement of even date herewith (the
"Series C Purchase Agreement");

         WHEREAS, it is a condition to the closing of the sale of Series C
Preferred Stock that, pursuant to the requirements of Section 4.2 of the
Original Agreement, the requisite parties to the Original Agreement amend and
restate the Original Agreement by entering into this Agreement or by executing a
written consent to amend and restate the Original Agreement (a "Consent");

         WHEREAS, the undersigned Prior Investors, and any Prior Investors
executing any Consent, desire to amend and restate in its entirety the Original
Agreement and to accept the rights and obligations created pursuant hereto in
lieu of their rights and obligations under the Original Agreement; and

         WHEREAS, this amendment and restatement of the Original Agreement shall
become effective, pursuant to the requirements of Section 4.2 of the Original
Agreement, upon the execution of this Agreement and/or a Consent by the Company
and the Prior Investors holding at least a majority of the Registrable
Securities, as defined in the Original Agreement.

         NOW, THEREFORE, in consideration of these mutual promises and covenants
set forth herein, the parties hereto agree to the terms and conditions set forth
below:

         1.       Information and Other Rights.

                  1.1     Financial Statements. So long as an Investor and its
affiliates hold at least 250,000 shares of Preferred Stock (or Common Stock
issued or issuable upon conversion of the Preferred Stock, or a combination
thereof), the Company shall provide to each Investor:

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                           (a) as soon as practicable after the end of each
fiscal year, and in any event within 90 days thereafter, an audited consolidated
balance sheet of the Company and its subsidiaries, if any, as of the end of such
fiscal year, and audited consolidated statements of income, stockholders' equity
and cash flows of the Company and its subsidiaries, if any, for such year,
prepared in accordance with generally accepted accounting principles ("GAAP")
and setting forth in each case in comparative form the figures for the previous
fiscal year, all in reasonable detail and all certified by a nationally
recognized public accounting firm.

                           (b) as soon as practicable after the end of each
quarter and in any event within 30 days thereafter, a consolidated balance sheet
of the Company and its subsidiaries, if any, as of the end of each such quarter,
and consolidated statements of income, stockholders' equity and cash flows of
the Company and its subsidiaries for such period and for the then current fiscal
year to date, and setting forth in each case in comparative form the figures for
corresponding periods in the previous fiscal year, and setting forth in
comparative form the budgeted figures for such period and for the then current
fiscal year then reported, prepared in accordance with GAAP consistently applied
with prior practice for earlier periods (with the exception of footnotes that
may be required by GAAP and provided that the foregoing shall not restrict the
right of the Company to change its accounting principles consistent with GAAP,
if the Board of Directors of the Company (the "Board of Directors") determines
that it is in the best interest of the Company to do so), subject to changes
resulting from year-end audit adjustments, all in reasonable detail and signed
by the principal financial or accounting officer of the Company.

                           (c) within thirty (30) days of the end of each month,
an unaudited consolidated balance sheet of the Company and its subsidiaries, if
any, as of the end of such month and consolidated statements of income and cash
flows for the end of such month, in reasonable detail, and setting forth in each
case in comparative form the figures for corresponding periods in the previous
fiscal year, and setting forth in comparative form the budgeted figures for such
period and for the then current fiscal year then reported, prepared in
accordance with GAAP consistently applied with prior practice for earlier
periods (with the exception of footnotes that may be required by GAAP and,
provided that, the foregoing shall not restrict the right of the Company to
change its accounting principles consistent with GAAP, if the Board of Directors
determines that it is in the best interest of the Company to do so), subject to
changes resulting from year-end audit adjustments, all in reasonable detail and
signed by the principal financial or accounting officer of the Company.

                           (d) as soon as practicable, but in any event not less
than thirty (30) days prior to the end of each fiscal year, a budget for the
next fiscal year, prepared on a monthly basis, including balance sheets and
sources and applications of funds statements for such months, and with
reasonable promptness after preparation, any other budgets or revised budgets
prepared by the Company; and

                           (e) with reasonable promptness, such other
information and data as such Investor may from time to time reasonably request.

                  1.2      Material Changes and Litigation. The Company shall
promptly notify the Investors of any material adverse change in the business,
prospects, assets or condition, financial

                                                                             -2-

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or otherwise, of the Company and of any litigation or governmental proceeding or
investigation brought or, to the Company's knowledge, threatened against the
Company or an officer, director, key employee or principal stockholder of the
Company which, if adversely determined, would have a material adverse effect on
the Company.

                  1.3      Access. The Company agrees to afford to the Investors
and their respective employees, counsel and other authorized representatives, as
well as to the directors elected solely by the holders of Preferred Stock (the
"Preferred Stock Directors"), upon reasonable prior request, free and full
access, during normal business hours, to all books, records and properties of
the Company and to all officers of the Company and those other employees of the
Company having responsibility for financial or accounting matters generally, for
any reasonable purpose whatsoever; provided, however, that such Investors and
Preferred Stock Directors shall agree to hold in confidence and trust and to act
in a fiduciary manner with respect to all information so provided; and, provided
further, that the Company reserves the right to withhold any information if
access to such information could adversely affect the attorney-client privilege
between the Company and its counsel or if the Board of Directors makes a good
faith determination that the requesting Investor is a competitor of the Company
or is acting on behalf of a competitor of the Company. Notwithstanding the
foregoing, an Investor may use information provided by the Company in connection
with the enforcement of its rights hereunder and its rights under any other
agreement between the Company and such Investor.

                  1.4      Proprietary Information Agreements. The Company
agrees to require each present or future employee or consultant of the Company
who is an executive officer of the Company or has duties in the areas of
technology, sales or marketing to enter into a Nondisclosure, Noncompetition and
Assignment of Inventions Agreement substantially in the form of Exhibit G to the
Series C Purchase Agreement unless otherwise approved by the Board of Directors.

                  1.5      Stock Vesting. Unless otherwise approved by the Board
of Directors, the Company shall not issue or grant any securities of the Company
to any officer, director, employee or consultant of the Company unless (i) such
securities are subject to vesting in equal installments over a five year period
commencing on the issuance or grant date (ii) such securities are subject to a
right of first refusal in favor of the Company and (iii) with respect to an
issuance or grant of securities of the Company that is equal to or greater than
1% of the capital stock of the Company on a fully-diluted basis, the recipient
enters into the Co-Sale Agreement as a "Founder" (as defined in the Co-Sale
Agreement). For purposes of this Agreement, "Co-Sale Agreement" means that
certain Second Amended and Restated Right of First Refusal and Co-Sale Agreement
dated as of April 10, 2003, among the Company, the Investors and certain other
stockholders of the Company, as the same may be amended from time to time.

                  1.6      Reserved Shares. The Company shall reserve and
maintain a sufficient number of shares of Common Stock for issuance upon
conversion of the outstanding shares of Preferred Stock.

                  1.7      Board Meetings. The Company agrees to use its best
efforts to cause a meeting of its Board of Directors to be held at least once
every calendar quarter.

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                  1.8      Qualified Small Business Stock. The Company covenants
that it will (i) comply with any applicable filing or reporting requirements
imposed by the Internal Revenue Code of 1986, as amended (the "Code"), any
regulations promulgated thereunder, on issuers of Qualified Small Business
Stock, as such term is defined in Section 1202(c) of the Code, and (ii) provide
to each Investor in writing any information or documentation reasonably
requested by such Investor so that such Investor may determine whether the
shares of Preferred Stock held by them constitute "Qualified Small Business
Stock" as defined in Section 1202(c) of the Code.

                  1.9      Termination of Covenants. The rights set forth in
this Article 1 shall terminate and be of no further force or effect upon the
closing of a Qualified IPO. For purposes of this Agreement, the term "Qualified
IPO" shall mean a firm commitment underwritten public offering of the Company's
securities pursuant to an effective registration statement filed by the Company
under the Securities Act of 1933, as amended, in which: (i) the aggregate gross
proceeds to the Company from such offering are not less than $30,000,000; and
(ii)(A) the public offering price per share (prior to underwriters' commissions
and discounts) is not less than $5.60 (appropriately adjusted to take account of
any stock split, stock dividend, combination of shares, or the like), or (B) the
holders of at least a majority of the shares of Preferred Stock then outstanding
voting on an as-converted basis elect to convert all shares of Preferred Stock
of the Company into shares of Common Stock of the Company.

         2.       Registration Rights.

                  2.1      Certain Definitions. As used in this Agreement, the
following terms shall have the following respective meanings:

                           (a) "Commission" shall mean the Securities and
Exchange Commission or any other federal agency at the time administering the
Securities Act.

                           (b) "Holder" shall mean an Investor holding
Registrable Securities or securities convertible or exercisable into Registrable
Securities and any person holding such securities to whom the rights under this
Article 2 have been transferred in accordance with Section 4.1 hereof.

                           (c) "Initiating Holders" shall mean any Holder or
Holders who in the aggregate hold at least 40% of the Registrable Securities.

                           (d) "Participating Holders" shall mean any Holder or
Holders who propose to distribute their securities through a registration
pursuant to this Article 2.

                           (e) "Registrable Securities" means (i) the Common
Stock issued or issuable upon conversion of Preferred Stock, (ii) any shares of
Common Stock, and any shares of Common Stock issued or issuable upon the
conversion or exercise of any other securities, acquired by the Investors
pursuant to Section 3 or pursuant to the Co-Sale Agreement, and (iii) any other
shares of Common Stock issued in respect of such shares (because of any stock
split, stock dividend, recapitalization, or similar event); provided, however,
that shares of Common Stock or other securities shall only be treated as
Registrable Securities for purposes of Section 2.3 hereof (A) if and so long as
they have not been sold to or through a broker or dealer or underwriter in a
public distribution or a public securities transaction, or (B) prior to the date

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such securities have been sold or are all available for immediate sale pursuant
to Rule 144(k) under the Securities Act.

                           (f) The terms "register," "registered" and
"registration" refer to a registration effected by preparing and filing a
registration statement in compliance with the Securities Act, and the
declaration or ordering of the effectiveness of such registration statement.

                           (g) "Registration Expenses" shall mean all expenses
incurred by the Company in complying with Sections 2.2, 2.3 and 2.4 hereof (but
excluding underwriting discounts and commissions) including, without limitation,
any additional registration and qualification fees and any additional fees and
disbursements of counsel to the Company that result from the inclusion of
securities held by the selling Holders in such registration.

                           (h) "Restricted Securities" shall mean the securities
of the Company required to bear a legend indicating that transfer is restricted
in the absence of registration.

                           (i) "Securities Act" shall mean the Securities Act of
1933, as amended, or any similar federal statute and the rules and regulations
of the Commission thereunder, all as the same shall be in effect at the time.

                           (j) "Selling Expenses" shall mean all underwriting
discounts, selling commissions and stock transfer taxes, if any, applicable to
the securities registered by the Holders.

                  2.2      Demand Registration.

                           (a) Request for Registration. In case the Company
shall receive from Initiating Holders a written request that the Company effect
any registration, qualification or compliance with respect to at least 40% of
the shares of Registrable Securities held by them, or a lesser percentage with
an expected aggregate offering price to the public of at least $5,000,000, the
Company will (1) within ten days of the receipt by the Company of such notice,
give written notice of the proposed registration, qualification or compliance to
all other Holders and (2) as soon as practicable (but within 100 days after
receipt of the request of the Initiating Holders), use its best efforts to
effect such registration, qualification or compliance (including, without
limitation, appropriate qualification under applicable blue sky or other state
securities laws and appropriate compliance with applicable regulations issued
under the Securities Act and any other governmental requirements or regulations)
as may be so requested and as would permit or facilitate the sale and
distribution of all or such portion of such Registrable Securities as are
specified in such request, together with all or such portion of the Registrable
Securities of any Holder or Holders joining in such request as are specified in
a written request received by the Company within 20 days after receipt of such
written notice from the Company; provided, however, that the Company shall not
be obligated to take any action to effect any such registration, qualification
or compliance pursuant to this Section 2.2(a):

                                    (i) In any particular jurisdiction in which
the Company would be required to execute a general consent to service of process
in effecting such registration, qualification or compliance unless the Company
is already subject to service in such jurisdiction and except as may be required
by the Securities Act;

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                                    (ii) Prior to the earlier of: (i) December
31, 2005, or (ii) six (6) months after the effective date of the Company's
initial underwritten public offering;

                                    (iii) During the period starting with the
date sixty (60) days prior to the Company's good faith estimate of the date of
filing of, and ending on the date six (6) months immediately following the
effective date of, any registration statement pertaining to securities of the
Company (other than a registration of securities in a Rule 145 transaction, with
respect to an employee benefit plan or with respect to the Company's first
registered public offering of its stock), provided that, the Company is actively
employing in good faith its best efforts to cause such registration statement to
become effective;

                                    (iv) After the Company has effected two
registrations pursuant to this Section 2.2(a), which registrations have been
declared or ordered effective;

                                    (v) If the Company shall furnish to such
Holders a certificate signed by the President of the Company stating that in the
good faith judgment of the Board of Directors it would be seriously detrimental
to the Company or its stockholders for a registration statement to be filed in
the near future, then the Company's obligation to use its best efforts to
register, qualify or comply under this Section 2.2 shall be deferred for a
period not to exceed 90 days from the date of receipt of written request from
the Initiating Holders; provided, however, that the Company shall not exercise
such right more than once in any twelve-month period.

                           (b) Underwriting. In the event that a registration
pursuant to this Section 2.2 is for a registered public offering involving an
underwriting, the Company shall so advise the Holders as part of the notice
given pursuant to Section 2.2(a). In such event, the right of any Holder to
registration pursuant to this Section 2.2 shall be conditioned upon such
Holder's participation in the underwriting arrangements required by this Section
2.2, and the inclusion of such Holder's Registrable Securities in the
underwriting to the extent requested shall be limited to the extent provided
herein.

         The Company shall, together with all Participating Holders, enter into
an underwriting agreement in customary form with the managing underwriter
selected for such underwriting by a majority of the Participating Holders and
reasonably acceptable to the Company. Notwithstanding any other provision of
this Section 2.2, if the managing underwriter advises the Company in writing
that marketing factors require a limitation of the number of shares to be
underwritten, then the Company shall so advise all Holders of Registrable
Securities and the number of shares of Registrable Securities that may be
included in the registration and underwriting shall be allocated among all
Holders thereof in proportion, as nearly as practicable, to the respective
amounts of Registrable Securities held by such Holders at the time of filing the
registration statement or in such other manner as shall be agreed to by the
Company and Holders of a majority of the Registrable Securities proposed to be
included in such registration; provided, however, that the number of shares of
Registrable Securities to be included in such underwriting shall not be reduced
unless all other securities are first entirely excluded from the underwriting.
No Registrable Securities excluded from the underwriting by reason of the
underwriter's marketing limitation shall be included in such registration. To
facilitate the allocation of shares in accordance with the above provisions, the
Company or the underwriters may round the number of shares allocated to any
Holder to the nearest 100 shares.

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<PAGE>

         If any Holder of Registrable Securities disapproves of the terms of the
underwriting, such Holder may elect to withdraw therefrom by written notice to
the Company, the managing underwriter and the Initiating Holders. The
Registrable Securities and/or other securities so withdrawn shall also be
withdrawn from registration, and such Registrable Securities shall not be
transferred in a public distribution prior to 180 days after the effective date
of such registration, or such other period of time as the underwriters may
require. If shares are withdrawn from registration, the Company shall offer to
all persons retaining the right to include securities in the registration the
right to include additional securities in the registration, with such shares
being allocated among all such Participating Holders in proportion, as nearly as
practicable, to the respective amounts of Registrable Securities held by such
Participating Holders at the time of filing the registration statement.

                  2.3      Piggyback Registration.

                           (a) Notice of Registration. If at any time or from
time to time the Company shall determine to register any of its securities,
either for its own account or the account of a security holder or holders, other
than a registration relating solely to employee benefit plans, a registration
relating solely to a Commission Rule 145 transaction, or a registration pursuant
to Section 2.2 hereof, the Company will (i) promptly give to each Holder written
notice thereof, and (ii) include in such registration (and any related
qualification under blue sky laws or other compliance), and in any underwriting
involved therein, all the Registrable Securities specified in a written request
or requests, made within 20 days after receipt of such written notice from the
Company, by any Holder.

                           (b) Underwriting. If the registration of which the
Company gives notice is for a registered public offering involving an
underwriting, the Company shall so advise the Holders as a part of the written
notice given pursuant to 2.3(a). In such event the right of any Holder to
registration pursuant to 2.3 shall be conditioned upon such Holder's
participation in such underwriting and the inclusion of Registrable Securities
in the underwriting to the extent provided herein. All Holders proposing to
distribute their securities through such underwriting shall (together with the
Company) enter into an underwriting agreement in customary form with the
managing underwriter selected for such underwriting by the Company.
Notwithstanding any other provision of this Section 2.3, if the managing
underwriter or Company determines that marketing factors require a limitation of
the number of shares to be underwritten, the managing underwriter may limit or
completely exclude the Registrable Securities and other securities to be
distributed through such underwriting, provided that, subsequent to the
Company's initial underwritten public offering, the Registrable Securities to be
included in such registration may not be limited to less than twenty-five
percent (25%) of the total number of securities to be included in such
registration. The Company shall so advise all Holders distributing their
securities through such underwriting of such limitation (or exclusion, if
applicable) and the number of shares of Registrable Securities that may be
included in the registration and underwriting shall be allocated (if applicable)
among all such Holders in proportion, as nearly as practicable, to the
respective amounts of Registrable Securities held by such Holders at the time of
filing the registration statement. To facilitate the allocation of shares in
accordance with the above provisions, the Company may round the number of shares
allocated to any Holder or other stockholder to the nearest 100 shares.

                                                                             -7-
<PAGE>

         If any Participating Holder disapproves of the terms of any such
underwriting, such Participating Holder may elect to withdraw therefrom by
written notice to the Company and the managing underwriter. Any securities
excluded or withdrawn from such underwriting shall be withdrawn from such
registration, and shall not be transferred in a public distribution prior to 180
days after the effective date of the registration statement relating thereto, or
such other period of time as the underwriters may require. If shares are
withdrawn from registration, the Company shall offer to all persons retaining
the right to include securities in the registration the right to include
additional securities in the registration, with such shares being allocated
among all such Participating Holders in proportion, as nearly as practicable, to
the respective amounts of Registrable Securities held by such Participating
Holders at the time of filing the registration statement.

                           (c) Right to Terminate Registration. The Company
shall have the right to terminate or withdraw any registration initiated by it
under this Section 2.3 prior to the effectiveness of such registration whether
or not any Holder has elected to include securities in such registration. The
Registration Expenses of such withdrawn registration shall be borne by the
Company in accordance with Section 2.5 hereof.

                  2.4      Registration on Form S-3. Following the Company's
initial public offering, the Company shall use commercially reasonable efforts
to become eligible to register offerings of securities on SEC Form S-3 or its
successor form ("Form S-3"). After the Company has qualified for the use of Form
S-3, Holders of the Registrable Securities then outstanding shall have the right
to request registration on Form S-3 (which request shall be in writing and shall
state the number of shares of Registrable Securities to be registered and the
intended method of disposition of shares by such Holders). If the Company
receives such a request then it shall use its best efforts to cause such shares
to be registered on Form S-3; provided that the Company shall not be obligated
to take any action to effect any such registration, qualification or compliance
pursuant to this Section 2.4(a):

                           (a) unless the Holders requesting registration
propose to dispose of Registrable Securities having an anticipated aggregate
price (after deduction of underwriting discounts and expenses of sale) of at
least $1,000,000;

                           (b) during the period starting with the date sixty
(60) days prior to the Company's estimated date of filing of, and ending on the
date six (6) months immediately following the effective date of, any
registration statement pertaining to securities of the Company (other than a
registration of securities in a Rule 145 transaction or with respect to an
employee benefit plan), provided that the Company is actively employing in good
faith its best efforts to cause such registration statement to become effective;

                           (c) more than twice in any twelve month period; or

                           (d) if the Company shall furnish to such Holder a
certificate signed by the President of the Company stating that in the good
faith judgment of the Board of Directors it would be seriously detrimental to
the Company or its stockholders for registration statements to be filed in the
near future, then the Company's obligation to use its best efforts to register,
qualify or comply under this Section 2.4 shall be deferred for a period not to
exceed 60 days from the

                                                                             -8-
<PAGE>

receipt of the request to file such registration by such Holder or Holders;
provided, however, that the Company shall not exercise such right more than once
in any twelve-month period.

                  2.5      Expenses of Registration. All Registration Expenses
incurred in connection with registrations pursuant to Section 2.3, the first two
registrations pursuant to Section 2.2 and the first four registrations pursuant
to Section 2.4 shall be borne by the Company. All Registration Expenses incurred
in connection with registrations pursuant to Section 2.4, after the first four
registrations initiated pursuant to such Section 2.4, shall be borne by the
holders of securities included in such registration pro rata among each other on
the basis of the number of shares so registered. All Selling Expenses relating
to securities registered on behalf of the Holders shall be borne by the holders
of securities included in such registration pro rata among each other on the
basis of the number of shares so registered.

                  2.6      Registration Procedures. In the case of each
registration, qualification or compliance effected by the Company pursuant to
this Article 2, the Company will keep each Holder advised in writing as to the
initiation of each registration, qualification and compliance and as to the
completion thereof. At its expense the Company will:

                           (a) Prepare and file with the Commission a
registration statement with respect to such securities and use its best efforts
to cause such registration statement to become and remain effective until the
distribution described in the Registration Statement has been completed;

                           (b) Prepare and file with the Commission such
amendments and supplements to such registration statement and the prospectus
used in connection with such registration statement as may be necessary to
comply with the provisions of the Securities Act with respect to the disposition
of all securities covered by such registration statement.

                           (c) Furnish to the Participating Holders and to the
underwriters of the securities being registered such reasonable number of copies
of the registration statement, preliminary prospectus, final prospectus and such
other documents as such Participating Holders and underwriters may reasonably
request in order to facilitate the public offering of such securities.

                           (d) Use commercially reasonable efforts to register
and qualify the securities covered by such registration statement under such
other securities or blue sky laws of such jurisdictions as shall be reasonably
requested by the Participating Holders, provided that the Company shall not be
required in connection therewith or as a condition thereto to qualify to do
business or to file a general consent to service of process in any such states
or jurisdictions, unless the Company is already subject to service in such
jurisdiction and except as may be required by the Securities Act.

                           (e) In the event of any underwritten public offering,
enter into and perform its obligations under an underwriting agreement, in usual
and customary form, with the managing underwriter of such offering. Each Holder
shall also enter into and perform its obligations under such an agreement.

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<PAGE>

                           (f) Notify each Participating Holder at any time when
a prospectus relating thereto is required to be delivered under the Securities
Act or upon the happening of any event as a result of which the prospectus
included in such registration statement, as then in effect, includes an untrue
statement of a material fact or omits to state a material fact required to be
stated therein or necessary to make the statements therein not misleading in the
light of the circumstances then existing.

                           (g) Cause all securities covered by such registration
statement to be listed on each securities exchange or authorized for quotation
on each automated quotation system on which similar securities issued by the
Company are then listed or authorized for quotation.

                           (h) Provide a transfer agent and registrar for all
securities covered by such registration statement and a CUSIP number for all
such Registrable Securities, in each case not later than the effective date of
such registration.

                           (i) Furnish, at the request of any Participating
Holder, on the date that the securities are delivered to the underwriters for
sale in connection with a registration being sold through underwriters, (i) an
opinion, dated such date, of the counsel representing the Company for the
purposes of such registration, in form and substance as is customarily given to
underwriters in an underwritten public offering, addressed to the underwriters,
if any, and to the Participating Holders and (ii) a letter dated such date, from
the independent certified public accountants of the Company, in form and
substance as is customarily given by independent certified public accountants to
underwriters in an underwritten public offering, addressed to the underwriters,
if any, and to the Holders requesting registration of Registrable Securities.

                           (j) Make available for inspection by any
Participating Holder, by any underwriter participating in any disposition to be
effected pursuant to such registration statement and by any attorney, accountant
or other agent retained by any such Participating Holder or any such
underwriter, all pertinent financial and other records and pertinent corporate
documents and properties of the Company, and cause all of the Company's
officers, directors and employees to supply all information reasonably requested
by any such Participating Holder, underwriter, attorney, accountant or agent in
connection with such registration statement.

                           (k) Use every reasonable effort to prevent the
issuance of any stop order suspending the effectiveness of such registration
statement or of any order preventing or suspending the use of any preliminary
prospectus and, if any such order is issued, to obtain the lifting thereof at
the earliest reasonable time.

                  2.7      Delay of Registration. No Holder shall have any right
to obtain or seek an injunction restraining or otherwise delaying any such
registration as the result of any controversy that might arise with respect to
the interpretation or implementation of this Article 2.

                  2.8      Indemnification. In the event any Registrable
Securities are included in a registration statement under this Article 2:

                           (a) To the extent permitted by law, the Company will
indemnify and hold harmless each Participating Holder, each of its officers,
directors, partners and legal

                                                                            -10-
<PAGE>

counsel, and each person controlling such Participating Holder within the
meaning of Section 15 of the Securities Act, with respect to which registration,
qualification or compliance has been effected pursuant to this Article 2, and
each underwriter, if any, and each person who controls any underwriter within
the meaning of Section 15 of the Securities Act, against all expenses, claims,
losses, damages or liabilities (or actions in respect thereof), including any of
the foregoing incurred in settlement of any litigation, commenced or threatened,
arising out of or based on any untrue statement (or alleged untrue statement) of
a material fact contained in any registration statement, prospectus, offering
circular or other document, or any amendment or supplement thereto, incident to
any such registration, qualification or compliance, or based on any omission (or
alleged omission) to state therein a material fact required to be stated therein
or necessary to make the statements therein, in light of the circumstances in
which they were made, not misleading, or any violation by the Company of the
Securities Act or any rule or regulation promulgated under the Securities Act
applicable to the Company in connection with any such registration,
qualification or compliance, and the Company will pay to each such Participating
Holder, each of its officers, directors, partners, and legal counsel and each
person controlling such Participating Holder, each such underwriter and each
person who controls any such underwriter, as incurred, any legal and any other
expenses reasonably incurred in connection with investigating, preparing or
defending any such claim, loss, damage, liability or action, provided that the
Company will not be liable in any such case to the extent that any such claim,
loss, damage, liability or expense arises out of or is based on any untrue
statement or omission or alleged untrue statement or omission, made in reliance
upon and in conformity with written information furnished to the Company by an
instrument duly executed by such Participating Holder, controlling person or
underwriter and stated to be specifically for use therein.

                           (b) To the extent permitted by law, each
Participating Holder will, if Registrable Securities held by such Participating
Holder are included in the securities as to which such registration,
qualification or compliance is being effected, indemnify and hold harmless the
Company, each of its directors, officers, and legal counsel, each underwriter,
if any, of the Company's securities covered by such a registration statement,
each person who controls the Company or such underwriter within the meaning of
Section 15 of the Securities Act, and each other Participating Holder, each of
its officers, directors, partners and legal counsel and each person controlling
such Participating Holder within the meaning of Section 15 of the Securities
Act, against all claims, losses, damages or liabilities (or actions in respect
thereof) arising out of or based on any untrue statement (or alleged untrue
statement) of a material fact contained in any such registration statement,
prospectus, offering circular or other document, or any omission (or alleged
omission) to state therein a material fact required to be stated therein or
necessary to make the statements therein, in light of the circumstances in which
they were made not misleading, and will pay the Company, such Participating
Holders, such directors, officers, persons, underwriters or control persons, as
incurred, any legal or any other expenses reasonably incurred in connection with
investigating or defending any such claim, loss, damage, liability or action, in
each case to the extent, but only to the extent, that such untrue statement (or
alleged untrue statement) or omission (or alleged omission) is made in such
registration statement, prospectus, offering circular or other document in
reliance upon and in conformity with written information furnished to the
Company by an instrument duly executed by such Holder and stated to be
specifically for use therein. Notwithstanding the foregoing, the liability of
each Holder under this subsection (b) shall be limited in an amount equal to the
proceeds to each such Holder of Registrable Securities sold as contemplated
herein, unless such liability resulted from willful

                                                                            -11-
<PAGE>

misconduct by such Holder. A Holder will not be required to enter into any
agreement or undertaking in connection with any registration under this Article
2 providing for any indemnification or contribution on the part of such Holder
greater than the Holder's obligations under this Section 2.8(b).

                           (c) Each party entitled to indemnification under this
Section 2.8 (the "Indemnified Party") shall give notice to the party required to
provide indemnification (the "Indemnifying Party") promptly after such
Indemnified Party has actual knowledge of any claim as to which indemnity may be
sought, and shall permit the Indemnifying Party to assume the defense of any
such claim or any litigation resulting therefrom, provided that counsel for the
Indemnifying Party, who shall conduct the defense of such claim or litigation,
shall be approved by the Indemnified Party (whose approval shall not be
unreasonably withheld), and the Indemnified Party may participate in such
defense at such party's expense, and, provided further, that the failure of any
Indemnified Party to give notice as provided herein shall not relieve the
Indemnifying Party of its obligations under this Article 2 unless the failure to
give such notice is materially prejudicial to an Indemnifying Party's ability to
defend such action and provided further, that the Indemnifying Party shall not
assume the defense for matters as to which there is a conflict of interest or
separate and different defenses but shall bear the expense of such defense
nevertheless. No Indemnifying Party, in the defense of any such claim or
litigation, shall, except with the consent of each Indemnified Party, consent to
entry of any judgment or enter into any settlement which does not include as an
unconditional term thereof the giving by the claimant or plaintiff to such
Indemnified Party of a release from all liability in respect to such claim or
litigation.

                           (d) If the indemnification provided for in this
Section 2.8 is held by a court of competent jurisdiction to be unavailable to an
indemnified party with respect to any loss, liability, claim, damage or expense
referred to therein, then the indemnifying party, in lieu of indemnifying such
indemnified party hereunder, shall contribute to the amount paid or payable by
such indemnified party as a result of such loss, liability, claim, damage, or
expense in such proportion as is appropriate to reflect the relative fault of
the indemnifying party on the one hand and of the indemnified party on the other
in connection with the statements or omissions that resulted in such loss,
liability, claim, damage or expense as well as any other relevant equitable
considerations; provided that, in no event shall any contribution by a Holder
under this Subsection (d) exceed the net proceeds from the offering received by
such Holder, except in the case of willful misconduct by such Holder. The
relative fault of the indemnifying party and of the indemnified party shall be
determined by reference to, among other things, whether the untrue or alleged
untrue statement of a material fact or the omission to state a material fact
relates to information supplied by the indemnifying party or by the indemnified
party and the parties' relative intent, knowledge, access to information, and
opportunity to correct or prevent such statement or omission.

                  2.9      Information by Holder. It shall be a condition
precedent to the obligations of the Company to take any action pursuant to this
Article 2 with respect to the Registrable Securities of any selling Holder that
such holder shall furnish to the Company such information regarding itself, the
Registrable Securities held by it, and the intended method of disposition of
such securities as shall be required to effect the registration of such Holder's
Registrable Securities.

                                                                            -12-
<PAGE>

                  2.10     Rule 144 Reporting. With a view to making available
to the Holders the benefits of Rule 144 and certain other rules and regulations
of the Commission which may at any time permit the sale of the Restricted
Securities to the public without registration, after such time as a public
market exists for the Common Stock of the Company, the Company agrees to use its
best efforts to:

                           (a) Make and keep public information available, as
those terms are defined in Rule 144 under the Securities Act, at all times after
the effective date that the Company becomes subject to the reporting
requirements of the Securities Act or the Securities Exchange Act of 1934, as
amended (the "Exchange Act"); and

                           (b) File with the Commission in a timely manner all
reports and other documents required of the Company under the Securities Act and
the Exchange Act (at any time after it has become subject to such reporting
requirements).

                           So long as an Investor owns any Restricted
Securities, upon such Investor's written request, the Company shall forthwith
furnish (i) a written statement by the Company as to its compliance with the
reporting requirements of said Rule 144 (at any time after 90 days after the
effective date of the first registration statement filed by the Company for an
offering of its securities to the general public), and of the Securities Act and
the Exchange Act (at any time after it has become subject to such reporting
requirements), (ii) a copy of the most recent annual or quarterly report of the
Company and (iii) such other reports and documents of the Company and other
information in the possession of or reasonably obtainable by the Company as an
Investor may reasonably request in availing itself of any rule or regulation of
the Commission allowing an Investor to sell any such securities without
registration.

                  2.11     Standoff Agreement. Each Holder agrees in connection
with the Company's initial underwritten public offering of the Company's
securities, upon request of the Company and the underwriters managing any
underwritten offering of the Company's securities, not to sell, make any short
sale of, loan, grant any option for the purchase of, or otherwise dispose of any
Registrable Securities (other than those included in the registration) without
the prior written consent of the Company or such underwriters, as the case may
be, for such period of time (not to exceed one hundred eighty (180) days) from
the effective date of such registration (the "Standoff Period")as may be
requested by the underwriters, provided that each officer, director and holder
of more than 1% of the outstanding capital stock of the Company shall be bound
by a similar agreement. In order to enforce the covenants set forth in this
Section 2.11, and until the expiration of Standoff Period:

                           (a) Each certificate held by a Holder representing
Registrable Securities shall bear the following legend:

                  "UPON THE REQUEST OF THE COMPANY OR THE UNDERWRITERS, THE
                  SECURITIES REPRESENTED BY THIS CERTIFICATE MAY NOT BE SOLD,
                  SHORT SOLD, LOANED, MADE SUBJECT TO AN OPTION TO PURCHASE SUCH
                  SECURITIES OR OTHERWISE DISPOSED OF FOR A PERIOD NOT TO EXCEED
                  180 DAYS FOLLOWING THE EFFECTIVE DATE OF A REGISTRATION
                  STATEMENT FILED BY THE COMPANY

                                                                            -13-
<PAGE>

                  FOR ITS INITIAL PUBLIC OFFERING, WITHOUT THE PRIOR WRITTEN
                  CONSENT OF THE COMPANY OR THE UNDERWRITERS."

                           (b) The Company may impose stop-transfer instructions
with respect to Registrable Securities of each Holder (and the shares or
securities of every other person subject to the restrictions set forth in this
Section 2.11). 2.12 Limitation on Subsequent Registration Rights. After the date
of this Agreement, the Company shall not, without the prior written consent of
the Holders of a majority of the Registrable Securities then outstanding, enter
into any agreement with any holder or prospective holder of any securities of
the Company that would grant such holder registration rights senior to those
granted to the Holders hereunder.

                  2.13     Mergers, etc. The Company shall not, directly or
indirectly, enter into any merger, consolidation or reorganization in which the
Company shall not be the surviving corporation unless the proposed surviving
corporation shall, prior to such merger, consolidation or reorganization, agree
in writing to assume the obligations of the Company under this Agreement, and
for that purpose references hereunder to "Registrable Securities" shall be
deemed to be references to the securities which the Holders would be entitled to
receive in exchange for Registrable Securities under any such merger,
consolidation or reorganization; provided, however, that the provisions of this
Agreement shall not apply in the event of any merger, consolidation or
reorganization in which the Corporation is not the surviving corporation if the
holders of Registrable Securities are entitled to receive in exchange therefor
(i) cash, or (ii) securities of the acquiring corporation which may be
immediately sold to the public without registration under the Securities Act.

                  2.14     Termination of Registration Rights. The rights
granted under this Article 2 shall terminate on the first to occur of (i) the
fifth anniversary of the consummation of the initial underwritten public
offering of the Company's securities pursuant to an effective registration
statement filed under the Securities Act, or (ii) as to any Holder, at such time
as such Holder is able to offer for sale all of its Registrable Securities
within a given three-month period pursuant to Rule 144 of the Securities Act.

         3.       Preemptive Rights.

                  3.1      General. Except for (i) Preferred Stock sold pursuant
to the Series Stock Purchase Agreement, (ii) securities issued in a public
offering pursuant to an effective registration statement under the Securities
Act in which all of the Preferred Stock is converted, (iii) securities issued
upon conversion of the Preferred Stock or other warrants or other convertible or
exercisable securities outstanding as of the date hereof, (iv) securities issued
in connection with any stock split or stock dividend of the Company,
recapitalizations or the like, (v) shares of Common Stock issued to employees,
officers, or directors of, or contractors, consultants or advisors to, the
Company pursuant to stock purchase or stock option plans, stock bonuses or
awards, contracts or other arrangements approved by the Company's Board of
Directors, (vi) shares of capital stock issued to a financial institution which
has loaned funds to the Company, the terms of which are approved by the Board of
Directors, (vii) shares of capital stock issued to equipment or real property
lessors, the terms of which are approved by the Board

                                                                            -14-
<PAGE>

of Directors, (viii) shares of capital stock issued in connection with the
acquisition of technology or licenses, the terms of which are approved by the
Board of Directors, or (ix) securities issued to non-financial corporations in
connection with a license, distribution, development, foundry or similar
"corporate partner" agreement, the terms of which are approved by the Board of
Directors, the Company will not, nor will it permit any subsidiary to, authorize
or issue any securities of the Company of any class or kind and will not
authorize, issue or grant any options, warrants, conversion rights or other
rights to purchase or acquire any shares of stock of the Company of any class
without offering the Investors the right of first refusal described below.

                  3.2      Right of First Offer. Each Investor that, along with
its affiliates, holds at least 250,000 shares of Preferred Stock (or Common
Stock issued or issuable upon conversion of the Preferred Stock, or a
combination thereof) shall have a right of first offer to purchase an amount of
securities of the Company of any class or kind which the Company proposes to
sell in a nonregistered private placement (other than the issuance of shares
contemplated by Section 3.1 above) ("Preemptive Securities") sufficient to
maintain such Investor's proportionate beneficial ownership interest in the
Company as set forth below. If the Company wishes to make any such sale of
Preemptive Securities, it shall give the Investors prior written notice of the
proposed sale. The notice shall set forth (i) the Company's bona fide intention
to offer Preemptive Securities and (ii) the material terms and conditions of the
proposed sale (including the number of shares to be offered and the price, if
any, for which the Company proposes to offer such shares), and shall constitute
an offer to sell Preemptive Securities to the Investors on such terms and
conditions. Any Investor may accept such offer by delivering a written notice of
acceptance (an "Acceptance Notice") to the Company within fifteen (15) days
after receipt of the Company's notice of the proposed sale. Investors exercising
their rights of first offer shall be entitled at their option to participate in
the purchase of Preemptive Securities on a pro rata basis to the extent
necessary to maintain such Investor's proportionate beneficial ownership
interest in the Company (such Investor's "Pro Rata Portion") (for purposes of
determining such Investor's Pro Rata Portion with respect to any issuance of
Preemptive Securities, any Investor or other security holder shall be treated as
owning that number of shares of Common Stock into which any outstanding
Preferred Stock may be converted, while the total Company interest will be
calculated on an as-converted to Common Stock basis, assuming full conversion
and exercise of all outstanding convertible or exercisable securities). The
Company shall, in writing, inform each Investor which elects to purchase its Pro
Rata Portion of Preemptive Securities of any other Investor's failure to do so,
in which case the Investors electing to purchase such shares of Preemptive
Securities shall have the right to purchase all of such shares on a pro rata
basis. If any Investor who elects to exercise its right of first offer does not
complete the purchase of such Preemptive Securities within fifteen (15) days
after delivery of its Acceptance Notice to the Company, the Company may complete
the sale of Preemptive Securities on the terms and conditions specified in the
Company's notice within the one hundred and twenty (120) day period following
the expiration of such fifteen (15) day period. If the Company does not enter
into an agreement for the sale of Preemptive Securities to the Investor pursuant
to a delivered Acceptance Notice within such fifteen (15) day period, or if the
Company does not otherwise consummate an agreement for the sale of Preemptive
Securities within such one hundred and twenty (120) day period, the right
provided hereunder shall be deemed to be revived and all future shares of
Preemptive Securities shall not be offered unless first reoffered to the
Investors in accordance with this Article 3. An Investor shall be entitled to
apportion the right of first offer hereby granted among itself and its partners
and affiliates in such proportions it deems appropriate.

                                                                            -15-
<PAGE>

                  3.3      Expiration of Right of First Offer. The right of
first offer granted under this Agreement shall terminate upon (i) the closing of
a Qualified IPO or (ii) as to any individual Investor, after such Investor fails
to purchase its full Pro Rata Portion of an issuance of Preemptive Securities.

         4.       Miscellaneous.

                  4.1      Transfer of Rights. This Agreement, and the rights
and obligations of each Investor hereunder, may be assigned by such Investor (i)
to any current or former partner, stockholder or other affiliate of such
Investor, (ii) to any person or entity to which at least 250,000 shares of
Registrable Securities are transferred by such Holder, or (iii) to any person or
entity to which all shares of Registrable Securities held by such Holder are
transferred, provided that, the transferee is not a competitor of the Company as
determined in good faith by the Board of Directors, the transferee or assignee
agrees in writing to all provisions contained in this Agreement and that such
transfer otherwise be effected in accordance with applicable securities laws.

                  4.2      Waivers and Amendments. With the written consent of
the holders of a majority of the Registrable Securities, the rights and
obligations of the Company and the holders of Registrable Securities under this
Agreement may be waived (either generally or in a particular instance, either
retroactively or prospectively, and either for a specified period of time or
indefinitely), and with the same consent, the Company, when authorized by
resolution of its Board of Directors, may enter into a supplementary agreement
for the purpose of adding additional parties and provisions to or changing in
any manner or eliminating any of the provisions of this Agreement. This
Agreement or any provision hereof may be changed, waived, discharged or
terminated only by a statement in writing signed by the party against which
enforcement of the change, waiver, discharge or termination is sought, except to
the extent provided in this Section 4.2; provided, however, and notwithstanding
anything herein to the contrary, that any Investor who purchases Shares at an
Additional Closing, as such terms are defined in the Series B Purchase
Agreement, in accordance with Section 2.2(b) of the Series B Purchase Agreement
may become a party to this Agreement without any amendment of this Agreement
pursuant to this Section 4.2 or any consent or approval of any other Investor.

                  4.3      Notices. All notices and other communications
required or permitted hereunder shall be in writing and shall be mailed by
registered or certified mail, postage prepaid, sent by facsimile or otherwise
delivered by hand or by courier addressed:

                           (a) If to an Investor, at the Investor's address or
facsimile number as shown on Exhibit A or at such other address as may have been
furnished to the Company in writing by the Investors;

                           (b) If to any other Holder, at such address or
facsimile number as shown in the Company's records, or, until any such Holder so
furnishes an address or facsimile number to the Company, then to and at the
address of the last holder of such Registrable Securities for which the Company
has contact information in its records; or

                                                                            -16-
<PAGE>

                           (c) If to the Company, one copy should be sent to its
address or facsimile number set forth on the Company's signature page of this
Agreement and addressed to the attention of the President, or at such other
address or facsimile number as the Company shall have furnished to the
Investors, with a copy to Michael J. O'Donnell, Esq., Wilson Sonsini Goodrich &
Rosati, 650 Page Mill Road, Palo Alto, California 94304.

         Each such notice or other communication shall for all purposes of this
Agreement be treated as effective or having been given when delivered if
delivered by hand or by courier, or, if sent by mail, at the earlier of its
receipt or 72 hours after the same has been deposited in a regularly maintained
receptacle for the deposit of the United States mail, addressed and mailed as
aforesaid or, if sent by facsimile, upon confirmation of facsimile transfer.

                  4.4      Descriptive Headings. The descriptive headings herein
have been inserted for convenience only and shall not be deemed to limit or
otherwise affect the construction of any provisions hereof.

                  4.5      Governing Law. This Agreement shall be governed by
and interpreted under the laws of the State of California as applied to
agreements among California residents, made and to be performed entirely within
the State of California.

                  4.6      Counterparts. This Agreement may be executed in one
or more counterparts, each of which shall for all purposes be deemed to be an
original and all of which shall constitute the same instrument, but only one of
which need be produced.

                  4.7      Expenses. If any action at law or in equity is
necessary to enforce or interpret the terms of this Agreement, the prevailing
party shall be entitled to reasonable attorney's fees, costs and necessary
disbursements in addition to any other relief to which such party may be
entitled.

                  4.8      Successors and Assigns. Except as otherwise expressly
provided in this Agreement, this Agreement shall benefit and bind the
successors, assigns, heirs, executors and administrators of the parties to this
Agreement.

                  4.9      Entire Agreement. This Agreement constitutes the full
and entire understanding and agreement between the parties with regard to the
subject matter of this Agreement.

                  4.10     Separability; Severability. Unless expressly provided
in this Agreement, the rights of each Investor under this Agreement are several
rights, not rights jointly held with any other Investors. Any invalidity,
illegality or limitation on the enforceability of this Agreement with respect to
any Investor shall not affect the validity, legality or enforceability of this
Agreement with respect to the other Investors. If any provision of this
Agreement is judicially determined to be invalid, illegal or unenforceable, the
validity, legality and enforceability of the remaining provisions shall not be
affected or impaired.

                  4.11     Stock Splits. All references to numbers of shares in
this Agreement shall be appropriately adjusted to reflect any stock dividend,
split, combination or other recapitalization of shares by the Company occurring
after the date of this Agreement.

                                                                            -17-
<PAGE>

                  4.12     Aggregation of Stock. All shares of Preferred Stock
held or acquired by affiliated entities or persons shall be aggregated together
for the purpose of determining the availability of any rights under this
Agreement.

                                                                            -18-
<PAGE>

         IN WITNESS WHEREOF, the parties have executed this Second Amended and
Restated Investors Rights' Agreement on the day and year first set forth above.

THE COMPANY:                          NANOSYS, INC.

                                      By: /s/ Lawrence A. Bock
                                          --------------------------------------
                                            Lawrence A. Bock, President

                                      Address: 200 Boston Avenue, Suite 4700
                                               Medford, MA 02156

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                               "INVESTORS"

                               ARCH VENTURE FUND V, L.P.

                               By: ARCH Venture Partners V, L.P.
                               Its: General Partner

                                    By: ARCH Venture Partners V, L.L.C.
                                    Its: General Partner

                                    By: /s/ Clint Bybee
                                        ----------------------------------------
                                            Managing Director

                               ARCH V ENTREPRENEURS FUND, L.P.

                               By: ARCH Venture Partners V, L.P.
                               Its: General Partner

                                    By:  ARCH Venture Partners V, L.L.C.
                                    Its: General Partner

                                    By: /s/ Clint Bybee
                                        ----------------------------------------
                                            Managing Director

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                             "INVESTORS"

                             POLARIS VENTURE PARTNERS III, L.P.

                             By: Polaris Venture Management Co. III, L.L.C.
                             Its: General Partner

                                  By: /s/ William E. Bilodeau
                                      ------------------------------------------
                                      William E. Bilodeau
                                      Attorney-in-fact

                             POLARIS VENTURE PARTNERS
                             ENTREPRENEURS' FUND III, L.P.

                             By: Polaris Venture Management Co. III, L.L.C.
                             Its: General Partner

                                  By: /s/ William E. Bilodeau
                                      ------------------------------------------
                                      William E. Bilodeau
                                      Attorney-in-fact

                             POLARIS VENTURE PARTNERS
                             FOUNDERS' FUND III, L.P.

                             By: Polaris Venture Management Co. III, L.L.C.
                             Its: General Partner

                                  By: /s/ William E. Bilodeau
                                      ------------------------------------------
                                      William E. Bilodeau
                                      Attorney-in-fact

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                              "INVESTORS"

                              VENROCK ASSOCIATES

                              By: /s/ Bryan E. Roberts
                                  ----------------------------------------------
                              Name: Bryan E. Roberts
                              Title: General Partner

                              VENROCK ASSOCIATES III, L.P.

                              By: Venrock Management III LLC
                              Its: General Partner

                                   By: /s/ Bryan E. Roberts
                                       -----------------------------------------
                                   Name:   Bryan E. Roberts
                                   Title:  Member

                              VENROCK ENTREPRENEURS FUND III, L.P.

                              By: VEF Management III LLC
                              Its: General Partner

                                   By: /s/ Bryan E. Roberts
                                       -----------------------------------------
                                   Name: Bryan E. Roberts
                                   Title: Member

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                CW VENTURES III, L.P.

                                By: /s/ Charles Hartman
                                    -------------------------------------------
                                    CW Partners IV, L.L.C.
                                    General Partner

                                CW VENTURES III - A CO-INVESTMENT
                                FUND, L.P.

                                By: /s/ Charles Hartman
                                    --------------------------------------------
                                    CW Partners IV, L.L.C.
                                    General Partner

                                J.P. MORGAN/CW VENTURES III
                                (NANOSYS), L.P.

                                By: /s/ Charles Hartman
                                    --------------------------------------------
                                    CW Partners IV, L.L.C.
                                    General Partner

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                PROSPECT VENTURE PARTNERS II, L.P.

                                By: Prospect Management Co. II, LLC
                                Its: General Partner

                                     By: /s/ James Tannanbaum
                                         ---------------------------------------
                                     Name: James Tananbaum
                                     Title: Managing Member

                                PROSPECT ASSOCIATES II, L.P.

                                By: Prospect Management Co. II, LLC
                                Its: General Partner

                                     By: /s/ James Tannanbaum
                                         ---------------------------------------
                                     Name: James Tananbaum
                                     Title: Managing Member

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                ALEXANDRIA EQUITIES, LLC, a Delaware
                                limited liability company

                                By: ALEXANDRIA REAL ESTATE
                                    EQUITIES, INC., a Maryland
                                    corporation, managing member

                                    By: /s/ Joel S. Marcus
                                        ----------------------------------------
                                        Joel S. Marcus, Chief Executive
                                        Officer

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                MCKENNA VENTURES, LP

                                By: /s/ Regis McKenna
                                    -------------------------------------------
                                Title: General Partner

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                WS INVESTMENT COMPANY, LLC
                                (2003A)

                                By: /s/ Michael J. O'Donnell
                                    --------------------------------------------
                                Title: Partner

                                WS INVESTMENT COMPANY, LLC
                               (2003C)

                                By: /s/ Michael J. O'Donnell
                                    --------------------------------------------
                                Title: Partner

                                /s/ Michael J. O'Donnell
                                ------------------------------------------------
                                Michael J. O'Donnell

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                /s/ R. Randolph Scott
                                ------------------------------------------------
                                R. Randolph Scott

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                CDIB BIOSCIENCE VENTURES I, INC.

                                By: /s/ Benny T. Hu
                                    --------------------------------------------
                                Name: Benny T. Hu
                                Title: Chairman

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                CHINA DEVELOPMENT INDUSTRIAL BANK INC.

                                By: /s/ Dr. Tze-Kaing Yang
                                    --------------------------------------------
                                Name: Dr. Tze-Kaing Yang
                                Title: President

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                QUANTA COMPUTER INC.

                                By: /s/ Barry Lam
                                    --------------------------------------------
                                Title: Chairman, Chief Executive Officer

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                CHIAO TUNG BANK CO., LTD

                                By: /s/ Maria D. H. Lu
                                    --------------------------------------------
                                Name: Maria D. H. Lu
                                Title: Sr. Vice President & General Manager

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                HARRIS & HARRIS GROUP, INC.

                                By: /s/ Mel Melsheimer
                                    --------------------------------------------
                                Name: Mel Melsheimer
                                Title: President

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                               "INVESTORS"

                               SAIC VENTURE CAPITAL CORPORATION

                               By: /s/ Kevin A. Werner
                                   ---------------------------------------------
                               Name:
                                    --------------------------------------------
                               Title:President, Managing Director

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                LUX VENTURES I LLC

                                By: LUX CAPITAL GROUP, LLC,
                                    Its Managing Member

                                    By: /s/ Josh Wolfe
                                        ---------------------------------------
                                    Name: Josh Wolfe
                                    Title: Managing Partner

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                 "INVESTORS"

                                INTEL CAPITAL CORPORATION

                                By: /s/ Mike Burns
                                    --------------------------------------------
                                Print Name:
                                           -------------------------------------
                                Title:Assistant Treasurer

                                HEALTHCARE FOCUS FUND, L.P.

                                By: ARCH Venture Partners V, L.P.
                                Its: General Partner

                                By: ARCH Venture Partners V, L.L.C.
                                Its: General Partner

                                By: /s/ Keith Rowe
                                    --------------------------------------------
                                    Managing Director

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                H.B. FULLER COMPANY

                                By: /s/ Raymond A. Tucker
                                    --------------------------------------------
                                    Raymond A. Tucker, Senior Vice
                                    President, Chief Financial Officer

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                EASTMAN KODAK COMPANY

                                By: /s/ James C. Stoffel
                                    --------------------------------------------
                                Name:
                                     -------------------------------------------
                                Title: Chief Technology Officer

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                "INVESTORS"

                                UOB HERMES ASIA TECHNOLOGY
                                FUND

                                By: /s/ Seah Kian Wee
                                    --------------------------------------------
                                Name:
                                     -------------------------------------------
                                Title: Deputy Managing Director of UOB
                                Venture Management Pte Ltd

                                UOB VENTURE TECHNOLOGY
                                INVESTMENTS LTD.

                                By: /s/ Seah Kian Wee
                                    -------------------------------------------
                                Name:
                                     -------------------------------------------
                                Title: Deputy Managing Director of UOB
                                Venture Management Pte Ltd

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                    "INVESTORS"

                                    THE TRUST AGREEMENT DATED 4/27/98, AMENDED
                                    AND RESTATED IN ITS ENTIRETY ON 1/15/99 AND
                                    FURTHER AMENDED ON 2/16/01, BY AND BETWEEN
                                    SASSON R. SOMEKH AND ETA SOMEKH AS TRUSTORS
                                    AND SASSON R. SOMEKH AND ETA SOMEKH AS
                                    CO-TRUSTEES (THE "TRUST") IS HEREBY AMENDED
                                    AND RESTATED IN ITS ENTIRETY BY THE TRUSTORS

                                    By: /s/ Sasson R. Somekh
                                        ----------------------------------------
                                    Name:
                                          --------------------------------------
                                    Title: Trustor, Co-Trustee

   (SIGNATURE PAGE TO SECOND AMENDED AND RESTATED INVESTORS' RIGHTS AGREEMENT)

<PAGE>

                                    EXHIBIT A

                              SCHEDULE OF INVESTORS

ARCH Venture Fund V. L.P.

ARCH V Entrepreneurs Fund, L.P.

CW Ventures III, L.P.

CW Ventures III - A Co-Investment Fund. L.P.

J.P. Morgan/CW Ventures III (Nanosys), L.P.

Venrock Associates

Venrock Associates III, L.P.

Venrock Entrepreneurs Fund III, L.P.

Polaris Venture Partners III, L.P.

Polaris Venture Partners Entrepreneurs' Fund III, L.P.

Polaris Venture Partners Founders' Fund III, L.P.

Prospect Venture Partners II, L.P.

Prospect Associates II, L.P.

Dr. Charles Lieber

Dr. Hongkun Park

Robert M. Metcalfe

Alan Chow C/F Tiffany Chow UGMA CA

Alan Chow C/F Harrison Chow UGMA CA

Alan Chow C/F Stephanie Chow UGMA CA

McKenna Ventures, LP

<PAGE>

Michael O'Donnell

R. Randolph Scott

Karen L. Vergura

WS Investment Company, LLC (2002A)

WS Investment Company, LLC (2003A)

WS Investment Company, LLC (2003C)

Alexandria Equities, LLC

China Development Industrial Bank Inc.

Quanta Computer Inc.

Chiao Tung Bank Co., Ltd.

CDIB Bioscience Ventures I, Inc.

Harris & Harris Group, Inc.

SAIC Venture Capital Corporation

Lux Ventures I LLC

Healthcare Focus Fund, L.P.

Intel Capital Corporation

H.B. Fuller Company

Eastman Kodak Company

UOB Hermes Asia Technology Fund

UOB Venture Technology Investments Ltd.

The Trust Agreement dtd 4/27/88, amended & restated in its entirety on 1/15/99,
and further amended on 2/16/01, by and between Sasson R. Somekh & Eta Somekh as
Trustors & Sasson R. Somekh & Eta Somekh as Co-Trustees<PAGE>

                                                                   EXHIBIT 4.2.1

       WAIVER OF RIGHT OF FIRST OFFER AND AMENDMENT NO.1 TO SECOND AMENDED
                    AND RESTATED INVESTORS' RIGHTS AGREEMENT

         WHEREAS, the undersigned In-Q-Tel, Inc., a Delaware corporation ("IQT")
and Nanosys, Inc., a Delaware corporation (the "Company"), have entered into a
certain Development Agreement(the "DA"), dated as of September 4, 2003, in
connection with which, among other things, the Company will issue to IQT and
In-Q-Tel Employee Fund (an affiliated entity of IQT and also undersigned hereto,
collectively the "Joining Parties") Warrants (the "Warrants") to purchase an
aggregate of up to 723,085 shares of the Company's Series C Preferred Stock,
$0.001 par value per share (the "Shares");

         WHEREAS, the parties hereto desire the Joining Parties to have certain
registration rights, rights of first offer and information rights pursuant to
that certain Second Amended and Restated Investors' Rights Agreement, dated as
of April 10, 2003, by and among the Company and the other parties named therein,
as the same may be amended and/or restated from time to time (the "Rights
Agreement"), and that the Joining Parties be added to the Rights Agreement as
parties thereto for the purpose of granting such registration rights, rights of
first offer and information rights; and

         WHEREAS, the parties hereto desire to waive any rights of first offer
under Section 3 of the Rights Agreement that such parties may have in connection
with the issuance of the Warrant; and

         WHEREAS, Section 4.2 of the Rights Agreement allows the amendment or
waiver of such Rights Agreement or any provision therein with the written
consent of the Company and the holders of at least a majority of the Registrable
Securities, as defined therein, outstanding (the "Majority Holders").

         NOW, THEREFORE, in consideration of the premises and for other good and
valuable consideration, the receipt and sufficiency of which is hereby mutually
acknowledged by the parties hereto, the parties hereby agree as follows:

         1. The Company and the requisite Majority Holders hereby: (i) consent
to the sale and issuance of the Warrants and the Shares (and all shares issuable
directly or indirectly upon conversion or exercise thereof); and (ii) hereby
waive their rights of first offer to purchase their pro-rata portion of the
Warrants and the Shares (and all shares issuable directly or indirectly upon
conversion or exercise thereof) pursuant to Section 3 of the Rights Agreement.

         2. The Company and the requisite Majority Holders hereby waive any
prior notice periods contained in the Rights Agreement that may pertain to this
Agreement.

         3. The Company and the requisite Majority Holders hereby consent to the
amendment of the Rights Agreement, and hereby amend the Rights Agreement, to add
the Joining Parties as Investors under the Rights Agreement with all the rights
and obligations (except as otherwise set forth in this Agreement) of Investors,
and that the shares of Common Stock issuable upon conversion of the Shares
underlying the Warrant shall be deemed to be Registrable Securities as defined
in the Rights Agreement.

<PAGE>

         4. Notwithstanding anything to the contrary in this Agreement, each of
the Joining Parties shall not: (i) be entitled to initiate or participate under
Section 2 of the Rights Agreement in any registration of the Company's
securities until after the conversion or exercise of such Joining Party's
Warrant; (ii) have or be deemed to have any rights of first offer pursuant to
Section 3 of the Rights Agreement until after the exercise or conversion of such
Joining Party's Warrant; (iii) have or be deemed to have any rights to materials
or information of the Company, rights to access to the Company's books, records
or properties or any other rights pursuant to Sections 1.1(e) or 1.3 of the
Rights Agreement; or (iv) have or be deemed to have the right to take part in
the initiation of a demand registration pursuant to Section 2.2 of the Rights
Agreement as "Initiating Holders" but shall be entitled after the conversion or
exercise of such Joining Party's Warrant to otherwise participate as a "Holder"
in a demand registration initiated under Section 2.2 by Investors other than the
Joining Parties. Prior to the date of any exercise or conversion of a Joining
Party's Warrant, and notwithstanding anything to the contrary herein or in the
Rights Agreement, such Joining Party shall for purposes of Sections 1.1(a), (b),
(c) and (d) of the Rights Agreement be deemed to hold the number of shares of
Series C Preferred Stock for which such Warrant is exercisable or may become
exercisable, provided that such Joining Party shall not be deemed to have any of
the other rights set forth in the Rights Agreement outside of Sections 1.1(a),
(b), (c) and (d) except as set forth in this Agreement.

         5. Notwithstanding anything to the contrary in this Agreement, this
Agreement shall terminate, and the Joining Parties, along with any transferees
of the Warrants, the Shares or the Common Stock underlying the Shares, shall no
longer be or be deemed to be Investors or holders of Registrable Securities
under the Rights Agreement if any of the following events occur: (i) the Warrant
terminates, or (ii) the Company does not receive an aggregate of at least
$2,000,000 from IQT pursuant to the DA by the 300th day following the date of
this Agreement.

         6. The Joining Parties hereby agree to be bound by the terms and
conditions of the Rights Agreement as set forth in this Agreement, provided
that, if a Joining Party transfers their Warrant, the Shares or the shares of
Common Stock issuable upon conversion of the Shares, such Joining Party shall
not be deemed to transfer (pursuant to Section 4.1 of the Rights Agreement or
otherwise) or possess any rights set forth in the Rights Agreement other than
the rights such Joining Party possesses pursuant to this Agreement, and no
transferee shall possess or be deemed to possess any rights under the Rights
Agreement other than the rights of such Joining Party hereunder. In addition to
the requirements for transfer set forth in Section 4.1 of the Rights Agreement,
no transfer of any Warrant, the Shares or the Common Stock underlying the Shares
to any transferee shall become effective until such transferee agrees in writing
to be bound by the terms and conditions of this Agreement as if such transferee
were a Joining Party hereunder by executing and delivering to the Company an
Agreement to be Bound, substantially in the form attached hereto as Attachment
A.

         7. Except as set forth herein, this Agreement shall be governed by the
provisions of Section 4 of the Rights Agreement, and shall be deemed to be a
part of the Rights Agreement.

         8. This Agreement may be executed in any number of separate
counterparts and all of said counterparts taken together shall be deemed to
constitute one and the same instrument.

                                                                             -2-
<PAGE>

         IN WITNESS WHEREOF, the parties have duly executed this Agreement as of
September 4, 2003.

                                 JOINING PARTIES:

                                 IN-Q-TEL, INC.

                                 By: /s/ Michael D. Griffin
                                     -------------------------------------------
                                 Name:
                                       -----------------------------------------
                                 Title: President, Chief Operating Officer

                                 IN-Q-TEL EMPLOYEE FUND

                                 By: /s/ Michael D. Griffin
                                     -------------------------------------------
                                 Name:
                                 Title: President, Chief Operating Officer

                                 COMPANY:

                                 NANOSYS, INC.

                                 By: /s/ Lawrence A. Bock
                                     -------------------------------------------
                                 Name:
                                       -----------------------------------------
                                 Title: President, Chief Executive Officer

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                           MAJORITY HOLDERS:

                                           /s/ Alan Chow
                                           -------------------------------------
                                           Alan Chow C/F Harrison Chow UGMA CA

                                           /s/ Alan Chow
                                           -------------------------------------
                                           Alan Chow C/F Stephanie Chow UGMA CA

                                           /s/ Alan Chow
                                           -------------------------------------
                                           Alan Chow C/F Tiffany Chow UGMA CA

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                    MAJORITY HOLDERS:

                                    ARCH VENTURE FUND V, L.P.

                                    By: ARCH Venture Partners V, L.P.
                                    Its: General Partner

                                          By: ARCH Venture Partners V, L.L.C.
                                          Its: General Partner

                                    By: /s/ Clint Bybee
                                        ----------------------------------------
                                        Managing Director

                                    ARCH V ENTREPRENEURS FUND, L.P.

                                    By: ARCH Venture Partners V, L.P.
                                    Its: General Partner

                                           By: ARCH Venture Partners V, L.L.C.
                                           Its: General Partner

                                    By: /s/ Clint Bybee
                                        ----------------------------------------
                                        Managing Director

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                         MAJORITY HOLDERS:

                         ALEXANDRIA EQUITIES, LLC, a Delaware limited
                         Liability company

                         By: Alexandria Real Estate Equities, Inc., a Maryland
                             corporation, managing member

                             By: /s/ Joel S. Marcus
                                 ---------------------------------
                                 Joel S. Marcus, Chief Executive Officer

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                         MAJORITY HOLDERS:

                         /s/ Jennifer K. Lieber
                         -------------------------------------------------------
                         Jennifer K. Lieber as Trustee of the Lieber
                         Family Trust u/d/dtd December 13, 2001

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                         MAJORITY HOLDERS:

                         MCKENNA VENTURES, L.P.

                         BY: /s/ Regis McKenna
                             ---------------------------------------------------
                         TITLE:  General Partner

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                MAJORITY HOLDERS:

                                CW VENTURES III, L.P.

                                By: /s/ Charles Hartman
                                    --------------------------------------------
                                    CW Partners IV, L.L.C.
                                    General Partner

                                CW VENTURES III - A CO-INVESTMENT
                                FUND, L.P.

                                By: /s/ Charles Hartman
                                    --------------------------------------------
                                    CW Partners IV, L.L.C.
                                    General Partner

                                J.P. MORGAN/CW VENTURES III
                                (NANOSYS), L.P.

                                By: /s/ Charles Hartman
                                    --------------------------------------------
                                    CW Partners IV, L.L.C.
                                    General Partner

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                      MAJORITY HOLDERS:

                                      /s/ Robert M. Metcalfe
                                      ------------------------------------------
                                      Robert M. Metcalfe

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                      MAJORITY HOLDERS:

                                      /s/ Charles Lieber
                                      ------------------------------------------
                                      Dr. Charles Lieber

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                      MAJORITY HOLDERS:

                                      __________________________________________
                                      Jennifer C. Snyder & Carolyn K. Hwang, as
                                      Trustees of the Park Family Trust u/d/dtd
                                      November 21, 2001

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                      MAJORITY HOLDERS:

                                      __________________________________________
                                      R. Randolph Scott

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                       MAJORITY HOLDERS:

                       POLARIS VENTURE PARTNERS III, L.P.

                       By: Polaris Venture Management Co. III, L.L.C.
                       Its: General Partner

                                 By: /s/ William E. Bilodeau
                                     -------------------------------------------
                                 William E. Bilodeau
                                 Attorney-in-fact

                       POLARIS VENTURE PARTNERS
                       ENTREPRENEURS' FUND III, L.P.

                       By: Polaris Venture Management Co. III, L.L.C.
                       Its: General Partner

                                 By: /s/ William E. Bilodeau
                                     -------------------------------------------
                                 William E. Bilodeau
                                 Attorney-in-fact

                       POLARIS VENTURE PARTNERS FOUNDERS'
                       FUND III, L.P.

                       By: Polaris Venture Management Co. III, L.L.C.
                       Its: General Partner

                                 By: /s/ William E. Bilodeau
                                     -------------------------------------------
                                 William E. Bilodeau
                                 Attorney-in-fact

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                               MAJORITY HOLDERS:

                               PROSPECT VENTURE PARTNERS II, L.P.

                               By:    Prospect Management Co. II, LLC
                               Its:   General Partner

                                      By: /s/ James Tananbaum
                                          --------------------------------------
                                      Name: James Tananbaum
                                      Title: Managing Member

                               PROSPECT ASSOCIATES II, L.P.

                               By: Prospect Management Co. II, LLC
                               Its: General Partner

                                      By: /s/ James Tanabaum
                                          --------------------------------------
                                      Name: James Tananbaum
                                      Title: Managing Member

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                               MAJORITY HOLDERS:

                               VENROCK ASSOCIATES

                               By: /s/ Bryan E. Roberts
                                   --------------------------------------------
                               Name: Bryan E. Roberts
                               Title: General Partner

                               VENROCK ASSOCIATES III, L.P.

                               By: Venrock Management III LLC
                                   Its: General Partner

                               By: /s/ Bryan E. Roberts
                                   ---------------------------------------------
                               Name: Bryan E. Roberts
                               Title: Member

                               VENROCK ENTREPRENEURS FUND III, L.P.

                               By: VEF Management III LLC
                                   Its: General Partner

                               By: /s/ Bryan E. Roberts
                                   --------------------------------------------
                               Name: Bryan E. Roberts
                               Title: Member

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     ___________________________________________
                                     Karen L. Vergura

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     WS INVESTMENT COMPANY, LLC (2002A)

                                     By: /s/ James Terranova
                                         ---------------------------------------
                                     Title: Manager

                                     WS INVESTMENT COMPANY, LLC (2003A)

                                     By: /s/ James Terranova
                                         --------------------------------------
                                     Title: Manager

                                     WS INVESTMENT COMPANY, LLC (2003C)

                                     By: /s/ James Terranova
                                         ---------------------------------------
                                     Title: Manager

                                     /s/ Michael J. O'Donnell
                                     -------------------------------------------
                                     Michael J. O'Donnell

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     CDIB BIOSCIENCE VENTURES I, INC.

                                     By: /s/ Benny T. Hu
                                         ---------------------------------------
                                     Name: Benny T. Hu
                                     Title: Chairman

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     CHINA DEVELOPMENT INDUSTRIAL BANK INC.

                                     By: _______________________________________
                                     Name: Dr. Tze-Kaing Yang
                                     Title: President

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     QUANTA COMPUTER INC.

                                     By: _______________________________________

                                     Title: ____________________________________

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     CHIAO TUNG BANK CO., LTD

                                     By: _______________________________________
                                     Name: Maria D.H. Lu
                                     Title: Sr. Vice President & General Manager

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     HARRIS & HARRIS GROUP, INC.

                                     By: /s/ Mel Melsheimer
                                         ---------------------------------------
                                     Name: Mel Melsheimer
                                     Title: President

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                    MAJORITY HOLDERS:

                                    SAIC VENTURE CAPITAL CORPORATION

                                    By:/s/ Gian Brown
                                       -----------------------------------------

                                    Name:
                                         ---------------------------------------
                                    Title: General Counsel

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     LUX VENTURES I LLC

                                     By: LUX CAPITAL GROUP, LLC,
                                         Its Managing Member

                                         By: /s/ Josh Wolfe
                                             -----------------------------------
                                         Name: Josh Wolfe
                                         Title: Managing Partner

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     INTEL CAPITAL CORPORATION

                                     By:
                                        ----------------------------------------
                                     Print Name:
                                                --------------------------------
                                     Title:
                                            ------------------------------------

                                     HEALTHCARE FOCUS FUND, L.P.

                                     By: ARCH Venture Partners V, L.P.
                                     Its: General Partner

                                     By: ARCH Venture Partners V, LLC
                                     Its: General Partner

                                     /s/ Clint Bybee
                                     -------------------------------------------
                                     Managing Director

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     H.B. FULLER COMPANY

                                     By: /s/ John A. Feenan
                                         ---------------------------------------
                                         John A. Feenan, Sr. Vice President,
                                         Chief Financial Officer

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     EASTMAN KODAK COMPANY

                                     By: /s/ Gary P. Van Graafeiland
                                         ---------------------------------------
                                     Name:
                                          --------------------------------------
                                     Title:Senior Vice President

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                     MAJORITY HOLDERS:

                                     UOB HERMES ASIA TECHNOLOGY FUND

                                     By: /s/ Seah Kian Wee
                                         ---------------------------------------
                                     Name:
                                          --------------------------------------
                                     Title: Deputy Managing Director
                                            UOB Venture Management Pte Ltd

                                     UOB VENTURE TECHNOLOGY INVESTMENTS LTD.

                                     By: /s/ Seah Kian Wee
                                         ---------------------------------------
                                     Name:
                                          --------------------------------------
                                     Title: Deputy Managing Director
                                            UOB Venture Management Pte Ltd

     [Signature Page to Waiver and Amendment to Investors' Rights Agreement]

<PAGE>

                                  ATTACHMENT A

                              AGREEMENT TO BE BOUND

         In connection with the transfer of the Warrant to purchase _________
shares of Series C Preferred Stock (the "Warrant") of Nanosys, Inc., a Delaware
corporation (the "Company"), __________ shares of Series C Preferred Stock of
the Company ("Preferred Shares"), and __________ shares of Common Stock of the
Company ("Common Shares") to the undersigned from ___________________ (the
"Transferor"), which Warrant, Preferred Shares and Common Shares are currently
subject to certain voting restrictions pursuant to the Waiver of Right of First
Offer and Amendment No.1 to Second Amended and Investors' Rights Agreement,
dated as of August __, 2003 (the "Amendment"), by and among the Company and the
Joining Parties, as defined in the Amendment attached hereto as Exhibit A, in
consideration of the Company permitting such transfer of the Warrant, Preferred
Shares and Common Shares to the undersigned, the undersigned hereby agrees by
executing this Agreement To Be Bound to be bound by and comply with all of the
provisions and obligations applicable to the Transferor contained in the
Amendment as if the undersigned were the Joining Party thereunder.

Date:  _____________________, 20__

By: __________________________
Name: ________________________
Title: _________________________

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