EXHIBIT 10.20(b)

CERTAIN CONFIDENTIAL PORTIONS OF THIS EXHIBIT WERE OMITTED BY MARKING SUCH
PORTIONS WITH ASTERISKS (THE "MARK").  THIS EXHIBIT HAS BEEN FILED SEPARATELY
WITH THE SECRETARY OF THE COMMISSION WITHOUT THE MARK PURSUANT TO THE COMPANY'S
APPLICATION REQUESTING CONFIDENTIAL TREATMENT.


                            -------------------------


                            INVESTOR RIGHTS AGREEMENT

                                ----------------


                                 October 5, 2000

                                       by

                                SKINMEDICA, INC.

                                       and

                         ADVANCED TISSUE SCIENCES, INC.





<PAGE>



                                TABLE OF CONTENTS

                                                                           Page
                                                                           ----

1.   Registration Rights.....................................................1
     1.1.     Definitions....................................................1
     1.2.     Request for Registration.......................................2
     1.3.     Company Registration...........................................3
     1.4.     Obligations of the Company.....................................3
     1.5.     Furnish Information............................................5
     1.6.     Expenses of This Section 1 Registration........................5
     1.7.     Underwriting Requirements......................................5
     1.8.     Delay of Registration..........................................6
     1.9.     Indemnification................................................6
     1.10.    Reports Under Securities Exchange Act of 1934..................7
     1.11.    Form S-3 Registration..........................................8
     1.12.    Assignment of Registration Rights..............................9
     1.13.    Limitations on Subsequent Registration Rights..................9
     1.14.    Termination of Registration Rights.............................9

2.   Covenants of the Company...............................................10
     2.1.     Right of First Negotiation....................................10
     2.2.     Right of First Offer..........................................11
     2.3.     Most Favorable Terms..........................................11
     2.4.     Termination of Certain Covenants..............................12

3.   Miscellaneous..........................................................12
         3.1.     Successors and Assigns....................................12
         3.2.     Governing Law.............................................12
         3.3.     Counterparts..............................................12
         3.4.     Titles and Subtitles......................................12
         3.5.     Notices...................................................12
         3.6.     Expenses..................................................12
         3.7.     Amendments and Waivers....................................13
         3.8.     Severability..............................................13
         3.9.     Aggregation of Stock......................................13
         3.10.    Entire Agreement; Amendment; Waiver.......................14


                                       i.

<PAGE>



                            INVESTOR RIGHTS AGREEMENT
                            -------------------------

     THIS INVESTOR RIGHTS AGREEMENT is made as of the 5th day of October, 2000,
by and between SkinMedica, Inc, a California corporation (the "Company"), and
ADVANCED TISSUE SCIENCES, INC., a Delaware corporation (the "Investor").

                                    RECITALS
                                    --------

     WHEREAS, the Company and the Investor are parties to the Development,
License and Supply Agreement of even date herewith (the "License and Supply
Agreement");

     WHEREAS, the Company and the Investor are parties to the Option to Purchase
Common Stock of even date herewith (the "Option");

     WHEREAS, in order to induce the Investor to enter into the License and
Supply Agreement, the Investor and the Company hereby agree that this Agreement
shall govern the rights of the Investor to cause the Company to register shares
of Common Stock issuable to the Investor upon exercise of the Option and certain
other matters as set forth herein and provide that these rights are the most
favorable rights offered to any other holders of the Company's securities.

     NOW, THEREFORE, THE PARTIES HEREBY AGREE AS FOLLOWS:

     1. Registration Rights. The Company covenants and agrees as follows:
        -------------------

        1.1. Definitions. For purposes of this Section 1:
             -----------

             (a) The term "Act" means the Securities Act of 1933, as amended.

             (b) The term "Form S-3" means such form under the Act as in effect
on the date hereof or any registration form under the Act subsequently adopted
by the SEC which permits inclusion or incorporation of substantial information
by reference to other documents filed by the Company with the SEC.

             (c) The term "Holder" means any person owning or having the right
to acquire Registrable Securities or any assignee thereof in accordance with
Section 1.12 hereof.

             (d) The term "1934 Act" shall mean the Securities Exchange Act of
1934, as amended.

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

             (f) The term "Registrable Securities" means the Common Stock
issuable or issued upon exercise of the Option.

             (g) The number of shares of "Registrable Securities then
outstanding" shall be determined by the number of shares of Common Stock
outstanding which are, and the number of shares of Common Stock issuable
pursuant to then exercisable or convertible securities which are, Registrable
Securities.


<PAGE>


             (h) The term "SEC" shall mean the Securities and Exchange
Commission.

        1.2. Request for Registration.
             ------------------------

             (a) If the Company shall receive at any time after six (6) months
after the effective date of the first registration statement for a public
offering of securities of the Company (other than a registration statement
relating either to the sale of securities to employees of the Company pursuant
to a stock option, stock purchase or similar plan or a SEC Rule 145
transaction), a written request from the Holders of a majority of the
Registrable Securities then outstanding that the Company file a registration
statement under the Act covering the registration of [**
    ] of the Registrable Securities then outstanding (or a lesser percent if the
anticipated aggregate offering price, net of underwriting discounts and
commissions, would exceed [**       ], then the Company shall:

                 (i) within ten (10) days of the receipt thereof, give written
notice of such request to all Holders; and

                 (ii) effect as soon as practicable, and in any event within 60
days of the receipt of such request, the registration under the Act of all
Registrable Securities which the Holders request to be registered, subject to
the limitations of subsection 1.2(b), within twenty (20) days of the mailing of
such notice by the Company in accordance with Section 3.5.

             (b) If the Holders initiating the registration request hereunder
("Initiating Holders") intend to distribute the Registrable Securities covered
by their request by means of an underwriting, they shall so advise the Company
as a part of their request made pursuant to subsection 1.2(a) and the Company
shall include such information in the written notice referred to in subsection
1.2(a). The underwriter will be selected by the Initiating Holders and shall be
reasonably acceptable to the Company. In such event, the right of any Holder to
include his Registrable Securities in such registration shall be conditioned
upon such Holder's participation in such underwriting and the inclusion of such
Holder's Registrable Securities in the underwriting (unless otherwise mutually
agreed by a majority in interest of the Initiating Holders and such Holder) to
the extent provided herein. All Holders proposing to distribute their securities
through such underwriting shall (together with the Company as provided in
subsection 1.4(e)) enter into an underwriting agreement in customary form with
the underwriter or underwriters selected for such underwriting. Notwithstanding
any other provision of this Section 1.2, if the underwriter advises the
Initiating Holders in writing that marketing factors require a limitation of the
number of shares to be underwritten, then the Initiating Holders shall so advise
all Holders of Registrable Securities which would otherwise be underwritten
pursuant hereto, and the number of shares of Registrable Securities that may be
included in the underwriting shall be allocated among all Holders thereof,
including the Initiating Holders, in proportion (as nearly as practicable) to
the amount of Registrable Securities of the Company owned by each Holder;
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.

             (c) Notwithstanding the foregoing, if the Company shall furnish to
Holders requesting a registration statement pursuant to this Section 1.2, a
certificate signed by the Chief Executive Officer of the Company stating that
in the good faith judgment of the Board of Directors of the Company, it would be
seriously detrimental to the Company and its shareholders for such registration
statement to be filed and it is therefore essential to defer the filing of such
registration statement, the Company shall have the right to defer taking action
with respect to such filing for a period of not more than 120 days after receipt
of the request of the Initiating Holders; provided, however, that the Company
may not utilize this right more than once in any twelve-month period.


                                       2.

<PAGE>


             (d) In addition, the Company shall not be obligated to effect, or
to take any action to effect, any registration pursuant to this Section 1.2:

                 (i) After the Company has effected one (1) registration
pursuant to this Section 1.2 and such registration has been declared or ordered
effective;

                 (ii) During the period starting with the date thirty (30) days
prior to the Company's good faith estimate of the date of filing of, and ending
on a date one hundred eighty (180) days after the effective date of, a
registration subject to Section 1.3 hereof; provided that the Company is
actively employing in good faith all reasonable efforts to cause such
registration statement to become effective; or

                 (iii) If the Initiating Holders propose to dispose of shares of
Registrable Securities that may be immediately registered on Form S-3 pursuant
to a request made pursuant to Section 1.11 below.

        1.3. Company Registration. If (but without any obligation to do so) the
             --------------------
Company proposes to register (including for this purpose a registration effected
by the Company for shareholders other than the Holders) any of its stock or
other securities under the Act in connection with the public offering of such
securities solely for cash (other than a registration relating solely to the
sale of securities to participants in a Company stock plan, a registration on
any form which does not include substantially the same information as would be
required to be included in a registration statement covering the sale of the
Registrable Securities or a registration in which the only Common Stock being
registered is Common Stock issuable upon conversion of debt securities which are
also being registered), the Company shall, at such time, promptly give each
Holder written notice of such registration. Upon the written request of each
Holder given within twenty (20) days after mailing of such notice by the Company
in accordance with Section 3.5, the Company shall, subject to the provisions of
Section 1.7, cause to be registered under the Act all of the Registrable
Securities that each such Holder has requested to be registered.

        1.4. Obligations of the Company. Whenever required under this Section 1
             --------------------------
to effect the registration of any Registrable Securities, the Company shall, as
expeditiously as reasonably possible:

             (a) Prepare and file with the SEC a registration statement with
respect to such Registrable Securities and use its best efforts to cause such
registration statement to become effective, and, upon the request of the Holders
of a majority of the Registrable Securities registered thereunder, keep such
registration statement effective for a period of up to one hundred twenty (120)
days or until the distribution contemplated in the Registration Statement has
been completed; provided, however, that (i) such 120-day period shall be
extended for a period of time equal to the period the Holder refrains from
selling any securities included in such registration at the request of an
underwriter of Common Stock (or other securities) of the Company; and (ii) in
the case of any registration of Registrable Securities on Form S-3 which are
intended to be offered on a continuous or delayed basis, such 120-day period
shall be extended, if necessary, to keep the registration statement effective
until all such Registrable Securities are sold, provided that Rule 415, or any
successor rule under the Act, permits an offering on a continuous or delayed
basis, and provided further that applicable rules under the Act governing the
obligation to file a post-effective amendment permit, in lieu of filing a
post-effective amendment which (I) includes any prospectus required by Section
10(a)(3) of the Act or (II) reflects facts or events representing a material or
fundamental change in the information set forth in the registration statement,
the incorporation by reference of information required to be included in (I) and
(II) above to be


                                       3.

<PAGE>


contained in periodic reports filed pursuant to Section 13 or 15(d) of the 1934
Act in the registration statement.

             (b) Prepare and file with the SEC 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
Act with respect to the disposition of all securities covered by such
registration statement.

             (c) Furnish to the Holders such numbers of copies of a prospectus,
including a preliminary prospectus, in conformity with the requirements of the
Act, and such other documents as they may reasonably request in order to
facilitate the disposition of Registrable Securities owned by them.

             (d) Use its best 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 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 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
participating in such underwriting shall also enter into and perform its
obligations under such an agreement.

             (f) Notify each Holder of Registrable Securities covered by such
registration statement at any time when a prospectus relating thereto is
required to be delivered under the Act of 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 such Registrable Securities registered pursuant
hereunder to be listed on each securities exchange on which similar securities
issued by the Company are then listed.

             (h) Provide a transfer agent and registrar for all Registrable
Securities registered pursuant hereunder 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 Holder requesting registration
of Registrable Securities pursuant to this Section 1, on the date that such
Registrable Securities are delivered to the underwriters for sale in connection
with a registration pursuant to this Section 1, if such securities are being
sold through underwriters, or, if such securities are not being sold through
underwriters, on the date that the registration statement with respect to such
securities becomes effective, (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 Holders requesting
registration of Registrable Securities 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


                                       4.

<PAGE>


public offering, addressed to the underwriters, if any, and to the Holders
requesting registration of Registrable Securities.

        1.5. Furnish Information. It shall be a condition precedent to the
             -------------------
obligations of the Company to take any action pursuant to this Section 1 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.

        1.6. Expenses of This Section 1 Registration. All expenses other than
             ---------------------------------------
underwriting discounts and commissions incurred in connection with
registrations, filings or qualifications pursuant to this Section 1, including
(without limitation) all registration, filing and qualification fees, printers'
and accounting fees, fees and disbursements of counsel for the Company
(including fees and disbursements of counsel for the Company in its capacity as
counsel to the selling Holders hereunder; if Company counsel does not make
itself available for this purpose, the Company will pay the reasonable fees and
disbursements of one counsel for the selling Holders) and the reasonable fees
and disbursements of one counsel for the selling Holders shall be borne by the
Company; provided, however, that the Company shall not be required to pay for
any expenses of any registration proceeding begun pursuant to Section 1.2 if the
registration request is subsequently withdrawn at the request of the Holders of
a majority of the Registrable Securities to be registered (in which case all
participating holders shall bear such expenses), unless the Holders of a
majority of the Registrable Securities agree to forfeit their right to one
demand registration pursuant to Section 1.2; provided further, however, that if
at the time of such withdrawal, the Holders have learned of a material adverse
change in the condition, business, or prospects of the Company from that known
to the Holders at the time of their request and have withdrawn the request with
reasonable promptness following disclosure by the Company of such material
adverse change, then the Holders shall not be required to pay any of such
expenses and shall retain their rights pursuant to Section 1.2.

        1.7. Underwriting Requirements. In connection with any offering
             -------------------------
involving an underwriting of shares of the Company's capital stock, the Company
shall not be required under Section 1.3 to include any of the Holders'
securities in such underwriting unless they accept the terms of the underwriting
as agreed upon between the Company and the underwriters selected by those
persons entitled to select the underwriters, and then only in such quantity as
the underwriters determine in their sole discretion will not jeopardize the
success of the offering by the Company. If the total amount of securities,
including Registrable Securities, requested by shareholders to be included in
such offering exceeds the amount of securities sold other than by the Company
that the underwriters determine in their sole discretion is compatible with the
success of the offering, then the Company shall be required to include in the
offering only that number of such securities, including Registrable Securities,
which the underwriters determine in their sole discretion will not jeopardize
the success of the offering (the securities so included to be apportioned pro
rata, according to the total amount of securities entitled to be included, among
the Holders' Registrable Securities first, and then, to the extent that the
number of the Holders' Registrable Securities to be included in such offering is
less that the total amount of securities entitled to be included therein,
apportioned pro rata, according to the total amount of securities entitled to be
included therein, among the other selling shareholders) but in no event shall
the amount of Registrable Securities of the selling Holders included in the
offering be reduced if the number of the Holders' Registrable Securities to be
included in such offering is less that the total amount of securities entitled
to be included therein.

        1.8. 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 Section 1.


                                       5.

<PAGE>


        1.9. Indemnification. In the event any Registrable Securities are
             ---------------
included in a registration statement under this Section 1:

             (a) To the extent permitted by law, the Company will indemnify and
hold harmless each Holder, any underwriter (as defined in the Act) for such
Holder and each person, if any, who controls such Holder or underwriter within
the meaning of the Act or the 1934 Act, against any losses, claims, damages, or
liabilities (joint or several) to which they may become subject under the Act,
or the 1934 Act or other federal or state law, insofar as such losses, claims,
damages, or liabilities (or actions in respect thereof) arise out of or are
based upon any of the following statements, omissions or violations
(collectively a "Violation"): (i) any untrue statement or alleged untrue
statement of a material fact contained in such registration statement, including
any preliminary prospectus or final prospectus contained therein or any
amendments or supplements thereto, (ii) the omission or alleged omission to
state therein a material fact required to be stated therein, or necessary to
make the statements therein not misleading, or (iii) any violation or alleged
violation by the Company of the Act, the 1934 Act, any state securities law or
any rule or regulation promulgated under the Act, or the 1934 Act or any state
securities law; and the Company will pay to each such Holder, underwriter or
controlling person, any legal or other expenses reasonably incurred by them in
connection with investigating or defending any such loss, claim, damage,
liability, or action; provided, however, that the indemnity agreement contained
in this subsection 1.9(a) shall not apply to amounts paid in settlement of any
such loss, claim, damage, liability, or action if such settlement is effected
without the consent of the Company (which consent shall not be unreasonably
withheld), nor shall the Company be liable in any such case for any such loss,
claim, damage, liability, or action to the extent that it arises out of or is
based upon a Violation which occurs in reliance upon and in conformity with
written information furnished expressly for use in connection with such
registration by any such Holder, underwriter or controlling person.

             (b) To the extent permitted by law, each selling Holder will
indemnify and hold harmless the Company, each of its directors, each of its
officers who has signed the registration statement, each person, if any, who
controls the Company within the meaning of the Act, any underwriter, any other
Holder selling securities in such registration statement and any controlling
person of any such underwriter or other Holder, against any losses, claims,
damages, or liabilities (joint or several) to which any of the foregoing persons
may become subject, under the Act, or the 1934 Act or other federal or state
law, insofar as such losses, claims, damages, or liabilities (or actions in
respect thereto) arise out of or are based upon any Violation, in each case to
the extent (and only to the extent) that such Violation occurs in reliance upon
and in conformity with written information furnished by such Holder expressly
for use in connection with such registration; and each such Holder will pay, any
legal or other expenses reasonably incurred by any person intended to be
indemnified pursuant to this subsection 1.9(b), in connection with investigating
or defending any such loss, claim, damage, liability, or action; provided,
however, that the indemnity agreement contained in this subsection 1.9(b) shall
not apply to amounts paid in settlement of any such loss, claim, damage,
liability or action if such settlement is effected without the consent of the
Holder, which consent shall not be unreasonably withheld; provided, that, in no
event shall any indemnity under this subsection 1.9(b) exceed the gross proceeds
from the offering received by such Holder.

             (c) Promptly after receipt by an indemnified party under this
Section 1.9 of notice of the commencement of any action (including any
governmental action), such indemnified party will, if a claim in respect thereof
is to be made against any indemnifying party under this Section 1.9, deliver to
the indemnifying party a written notice of the commencement thereof and the
indemnifying party shall have the right to participate in, and, to the extent
the indemnifying party so desires, jointly with any other indemnifying party
similarly noticed, to assume the defense thereof with counsel mutually
satisfactory to the parties; provided, however, that an indemnified party
(together with all other indemnified parties which may be represented without
conflict by one counsel) shall have the


                                       6.

<PAGE>


right to retain one separate counsel, with the fees and expenses to be paid by
the indemnifying party, if representation of such indemnified party by the
counsel retained by the indemnifying party would be inappropriate due to actual
or potential differing interests between such indemnified party and any other
party represented by such counsel in such proceeding. The failure to deliver
written notice to the indemnifying party within a reasonable time of the
commencement of any such action, if prejudicial to its ability to defend such
action, shall relieve such indemnifying party of any liability to the
indemnified party under this Section 1.9, but the omission so to deliver written
notice to the indemnifying party will not relieve it of any liability that it
may have to any indemnified party otherwise than under this Section 1.9.

             (d) If the indemnification provided for in this Section 1.9 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. 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.

             (e) Notwithstanding the foregoing, to the extent that the
provisions on indemnification and contribution contained in the underwriting
agreement entered into in connection with the underwritten public offering are
in conflict with the foregoing provisions, the provisions in the underwriting
agreement shall control.

             (f) The obligations of the Company and Holders under this Section
1.9 shall survive the completion of any offering of Registrable Securities in a
registration statement under this Section 1, and otherwise.

        1.10. Reports Under Securities Exchange Act of 1934. With a view to
              ---------------------------------------------
making available to the Holders the benefits of Rule 144 promulgated under the
Act and any other rule or regulation of the SEC that may at any time permit a
Holder to sell securities of the Company to the public without registration or
pursuant to a registration on Form S-3, the Company agrees to:

             (a) make and keep public information available, as those terms are
understood and defined in SEC Rule 144, at all times after ninety (90) days
after the effective date of the first registration statement filed by the
Company for the offering of its securities to the general public;

             (b) take such action, including the voluntary registration of its
Common Stock under Section 12 of the 1934 Act, as is necessary to enable the
Holders to utilize Form S-3 for the sale of their Registrable Securities, such
action to be taken as soon as practicable after the end of the fiscal year in
which the first registration statement filed by the Company for the offering of
its securities to the general public is declared effective;

             (c) file with the SEC in a timely manner all reports and other
documents required of the Company under the Act and the 1934 Act; and


                                       7.

<PAGE>


             (d) furnish to any Holder, so long as the Holder owns any
Registrable Securities, forthwith upon request (i) a written statement by the
Company that it has complied with the reporting requirements of SEC Rule 144
(at any time after ninety (90) days after the effective date of the first
registration statement filed by the Company), the Act and the 1934 Act (at any
time after it has become subject to such reporting requirements), or that it
qualifies as a registrant whose securities may be resold pursuant to Form S-3
(at any time after it so qualifies), (ii) a copy of the most recent annual or
quarterly report of the Company and such other reports and documents so filed by
the Company, and (iii) such other information as may be reasonably requested in
availing any Holder of any rule or regulation of the SEC which permits the
selling of any such securities without registration or pursuant to such form.

        1.11. Form S-3 Registration. In case the Company shall receive from any
              ---------------------
Holder or Holders a written request or requests that the Company effect a
registration on Form S-3 and any related qualification or compliance with
respect to all or a part of the Registrable Securities owned by such Holder or
Holders, the Company will:

             (a) promptly give written notice of the proposed registration, and
any related qualification or compliance, to all other Holders; and

             (b) as soon as practicable, effect such registration and all such
qualifications and compliances as may be so requested and as would permit or
facilitate the sale and distribution of all or such portion of such Holder's or
Holders' Registrable Securities as are specified in such request, together with
all or such portion of the Registrable Securities of any other Holder or Holders
joining in such request as are specified in a written request given within 15
days after receipt of such written notice from the Company; provided, however,
that the Company shall not be obligated to effect any such registration,
qualification or compliance, pursuant to this Section 1.11: (1) if Form S-3 is
not available for such offering by the Holders; (2) if the Holders, together
with the holders of any other securities of the Company entitled to inclusion in
such registration, propose to sell Registrable Securities and such other
securities (if any) at an aggregate price to the public (net of any
underwriters' discounts or commissions) of less than [**     ]; (3) if the
Company shall furnish to the Holders a certificate signed by the President of
the Company stating that in the good faith judgment of the Board of Directors of
the Company, it would be seriously detrimental to the Company and its
shareholders for such Form S-3 Registration to be effected at such time, in
which event the Company shall have the right to defer the filing of the Form S-3
registration statement for a period of not more than 60 days after receipt of
the request of the Holder or Holders under this Section 1.11; provided, however,
that the Company shall not utilize this right more than once in any twelve month
period; (4) if the Company has, within the twelve (12) month period preceding
the date of such request, already effected two registrations on Form S-3 for the
Holders pursuant to this Section 1.11; or (5) in any particular jurisdiction in
which the Company would be required to qualify to do business or to execute a
general consent to service of process in effecting such registration,
qualification or compliance.

             (c) Subject to the foregoing, the Company shall file a registration
statement covering the Registrable Securities and other securities so requested
to be registered as soon as practicable after receipt of the request or requests
of the Holders. Registrations effected pursuant to this Section 1.11 shall not
be counted as demands for registration or registrations effected pursuant to
Sections 1.2 or 1.3, respectively.

        1.12. Assignment of Registration Rights. The rights to cause the Company
              ---------------------------------
to register Registrable Securities pursuant to this Section 1 may be assigned
(but only with all related obligations) by a Holder to a transferee or assignee
of such securities, provided: (a) the Company is, within a reasonable time after
such transfer, furnished with written notice of the name and address of such


                                       8.

<PAGE>


transferee or assignee and the securities with respect to which such
registration rights are being assigned; (b) such transferee or assignee agrees
in writing to be bound by and subject to the terms and conditions of this
Agreement, including without limitation the provisions of Section 1.13 below;
and (c) such assignment shall be effective only if immediately following such
transfer the further disposition of such securities by the transferee or
assignee is restricted under the Act.

        1.13. Limitations on Subsequent Registration Rights. From and after the
              ---------------------------------------------
date of this Agreement, the Company shall not, without the prior written consent
of the Holders of a majority of the outstanding Registrable Securities, enter
into any agreement with any holder or prospective holder of any securities of
the Company which would allow such holder or prospective holder (a) to include
such securities in any registration filed under Section 1.2 hereof, unless under
the terms of such agreement, such holder or prospective holder may include such
securities in any such registration only to the extent that the inclusion of his
securities will not reduce the amount of the Registrable Securities of the
Holders which is included or (b) to make a demand registration which could
result in such registration statement being declared effective prior to the
earlier of either of the dates set forth in subsection 1.2(a) or within one
hundred twenty (120) days of the effective date of any registration effected
pursuant to Section 1.2.

        1.14. Termination of Registration Rights.
              ----------------------------------

             (a) No Holder shall be entitled to exercise any right provided for
in this Section 1 after five (5) years following the consummation of the sale of
securities pursuant to a registration statement filed by the Company under the
Act in connection with the initial firm commitment underwritten offering of its
securities to the general public.

             (b) In addition, the right of any Holder to request registration or
inclusion in any registration pursuant to Section 1.3 shall terminate on the
closing of the first Company-initiated registered public offering of Common
Stock of the Company if all shares of Registrable Securities held or entitled to
be held upon conversion by such Holder may immediately be sold under Rule 144
during any 90-day period, or on such date after the closing of the first
Company-initiated registered public offering of Common Stock of the Company as
all shares of Registrable Securities held or entitled to be held upon conversion
by such Holder may immediately be sold under Rule 144 during any 90-day period;
provided, however, that the provisions of this Section 1.14(b) shall not apply
to any Holder who owns more than two percent (2%) of the Company's outstanding
stock until such time as such Holder owns less than two percent (2%) of the
outstanding stock of the Company.

     2. Covenants of the Company.
        ------------------------

        2.1. Right of First Negotiation. After the first year of this Investor
             --------------------------
Rights Agreement, subject to the terms and conditions specified in this Section
2.1, the Company hereby grants to the Investor, so long as it remains a
beneficial holder of Registrable Securities, a right of first negotiation with
respect to future offers by the Company of its Shares (as hereinafter defined).
Each time the Company proposes to negotiate an offer of any shares of, or
securities convertible into or exercisable for any shares of, any class of its
capital stock ("Shares"), the Company shall first negotiate with the Investor
for an offering of the Shares in accordance with the following provisions:

             (a) The Company shall deliver a notice by certified mail
("Negotiation Notice") to the Investor stating its bona fide intention to
negotiate an offer of such Shares.

             (b) Within 15 calendar days after receipt of the Negotiation
Notice, the Investor may elect to enter into negotiations to purchase or obtain
the Shares.


                                       9.

<PAGE>


             (c) If the Investor does not chose to negotiate to purchase or
obtain the Shares, then during the 30-day period following the expiration of the
period provided in subsection 2.1(b) hereof, the Company may enter into
negotiations to offer the Shares to any third party or parties. If the Company
negotiates an offer of the Shares, then the Company shall comply with its
obligations under Section 2.2 below. If the Company does not negotiate an offer
of the Shares within such period, the right provided under this Section 2.1
shall be deemed to be revived and negotiations with respect to future offers of
the Shares shall not be entered into unless first reoffered to the Investor in
accordance herewith.

             (d) The right of first negotiation in this Section 2.1 shall not be
applicable (i) to any negotiations in connection with the issuance or sale of
shares of common stock (or options therefor) to employees for the primary
purpose of soliciting or retaining their employment, pursuant to a stock option,
stock purchase or stock bonus plan, or (ii) to any negotiations in connection
with a bona fide, firmly underwritten public offering of shares of common stock,
registered under the Act pursuant to a registration statement on Form S-1, at an
offering price of at least $10.00 per share (appropriately adjusted for any
stock split, dividend, combination or other recapitalization) and $75,000,000 in
the aggregate.

             (e) The right of first negotiation set forth in this Section 2.1
may not be assigned or transferred, except that such right is assignable by the
Investor to (i) any wholly owned subsidiary or parent of, or to any corporation
or entity that is, within the meaning of the Act, controlling, controlled by or
under common control with, the Investor, or (ii) any business organization which
the Investor consolidates with, or merges into, or to which the Investor sells
or conveys all of the Investor's stock or all or substantially all of the assets
of the Investor.

        2.2. Right of First Offer. After the first year of this Investor Rights
             --------------------
Agreement, subject to the terms and conditions specified in Section 2.1 above
and this Section 2.2, the Company hereby grants to the Investor, provided it
owns any Registrable Securities or the Option, a right of first offer with
respect to future sales by the Company of its Shares. Each time the Company
proposes to offer any Shares, the Company shall first make an offering of such
Shares to the Investor in accordance with the following provisions:

             (a) The Company shall deliver a notice by certified mail ("Offer
Notice") to the Investor stating (i) its bona fide intention to offer such
Shares, (ii) the number of such Shares to be offered, and (iii) the price and
terms, if any, upon which it proposes to offer such Shares.

             (b) Within 30 calendar days after receipt of the Offer Notice, the
Investor may elect to purchase or obtain, at the price and on the terms
specified in the Offer Notice, up to that portion of such Shares which equals
the proportion that the number of shares of common stock issued and held, or
issuable upon exercise of the Option then held by the Investor bears to the
total number of shares of common stock of the Company then outstanding (assuming
full conversion and exercise of all convertible or exercisable securities).

             (c) If all Shares which Investor is entitled to obtain pursuant to
subsection 2.2(b) are not elected to be obtained as provided in subsection
2.2(b) hereof, the Company may, during the 30-day period following the
expiration of the period provided in subsection 2.2(b) hereof, offer the
remaining unsubscribed portion of such Shares to any person or persons at a
price not less than, and upon terms no more favorable to the offeree than those
specified in the Offer Notice. If the Company does not enter into an agreement
for the sale of the Shares within such period, or if such agreement is not
consummated within 30 days of the execution thereof, the right provided
hereunder shall be deemed to be revived and such Shares shall not be offered
unless first reoffered to the Investor in accordance herewith.


                                      10.

<PAGE>


             (d) The right of first offer in this Section 2.2 shall not be
applicable (i) to the issuance or sale of shares of common stock (or options
therefor) to employees for the primary purpose of soliciting or retaining their
employment, pursuant to a stock option, stock purchase or stock bonus plan, or
(ii) to or after consummation of a bona fide, firmly underwritten public
offering of shares of common stock, registered under the Act pursuant to a
registration statement on Form S-1, at an offering price of at least $10.00 per
share (appropriately adjusted for any stock split, dividend, combination or
other recapitalization) and $75,000,000 in the aggregate.

             (e) The right of first offer set forth in this Section 2.2 may not
be assigned or transferred, except that such right is assignable by the Investor
to (i) any wholly owned subsidiary or parent of, or to any corporation or entity
that is, within the meaning of the Act, controlling, controlled by or under
common control with, the Investor, or (ii) any business organization which the
Investor consolidates with, or merges into, or to which the Investor sells or
conveys all of the Investor's stock or all or substantially all of the assets of
the Investor.

        2.3. Most Favorable Terms. The Company agrees that in the event the
             --------------------
Company offers registration and any similar rights provided under this Agreement
to any third party holder of the Company's securities which are superior or more
favorable than the rights granted to Investor hereunder, then the Company shall
promptly and at its sole expense take all necessary actions to amend or modify
this Agreement in order to provide Investor with such superior or more favorable
rights.

        2.4. Termination of Certain Covenants. The covenants set forth in
             --------------------------------
Sections 2.1 and 2.2 shall terminate and be of no further force or effect upon
the earlier of (a) the consummation of the sale of securities pursuant to a
registration statement filed by the Company under the Act in connection with the
firm commitment underwritten offering of its securities to the general public,
or (b) the expiration or termination of the License and Supply Agreement as a
result of default on the License and Supply Agreement by Investor.

     3. Miscellaneous.
        -------------

        3.1. Successors and Assigns. Except as otherwise provided herein, the
             ----------------------
terms and conditions of this Agreement shall inure to the benefit of and be
binding upon the respective successors and assigns of the parties (including
transferees of any shares of Registrable Securities). Nothing in this Agreement,
express or implied, is intended to confer upon any party other than the parties
hereto or their respective successors and assigns any rights, remedies,
obligations, or liabilities under or by reason of this Agreement, except as
expressly provided in this Agreement.

        3.2. Governing Law. This Agreement shall be governed by and construed
             -------------
under the laws of the State of California as applied to agreements among
California residents entered into and to be performed entirely within
California.

        3.3. Counterparts. This Agreement may be executed in two or more
             ------------
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

        3.4. Titles and Subtitles. The titles and subtitles used in this
             --------------------
Agreement are used for convenience only and are not to be considered in
construing or interpreting this Agreement.

        3.5. Notices. Unless otherwise provided, any notice required or
             -------
permitted under this Agreement shall be given in writing and shall be deemed
effectively given upon personal delivery to the party to be notified or upon
deposit with the United States Post Office, by registered or


                                      11.

<PAGE>


certified mail, postage prepaid and addressed to the party to be notified at the
address indicated for such party on the signature page hereof, or at such other
address as such party may designate by ten (10) days' advance written notice to
the other parties.

        3.6. 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 attorneys' fees, costs and necessary disbursements in addition to
any other relief to which such party may be entitled.

        3.7. Amendments and Waivers. Any term of this Agreement may be amended
             ----------------------
and the observance of any term of this Agreement may be waived (either generally
or in a particular instance and either retroactively or prospectively), only
with the written consent of the Company and the holders of a majority of the
Registrable Securities then outstanding. Any amendment or waiver effected in
accordance with this Section 3.7 shall be binding upon each holder of any
Registrable Securities then outstanding, each future holder of all such
Registrable Securities, and the Company.

        3.8. Severability. If one or more provisions of this Agreement are held
             ------------
to be unenforceable under applicable law, such provision shall be excluded from
this Agreement and the balance of the Agreement shall be interpreted as if such
provision were so excluded and shall be enforceable in accordance with its
terms.

        3.9. Aggregation of Stock. All shares of Registrable Securities 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.


                                      12.

<PAGE>


        3.10. Entire Agreement; Amendment; Waiver. This Agreement (including the
              -----------------------------------
Exhibits hereto, if any) constitutes the full and entire understanding and
agreement between the parties with regard to the subjects hereof and thereof.

     IN WITNESS WHEREOF, the parties have executed this Agreement as of the date
first above written.

                                      SKINMEDICA, INC.

                                      By: /s/ Thomas V. Compton
                                         -------------------------------

                                      Its: CEO
                                          ------------------------------

                                      Name: Thomas V. Compton
                                           -----------------------------

                              Address: 2380 Camino Vida Roble, Suite C
                                      ----------------------------------
                                       Carlsbad, CA 92009
                                      ----------------------------------



                                      ADVANCED TISSUE SCIENCES, INC.


                                      By:  /s/ Gail K. Naughton, Ph.D.
                                         -------------------------------

                                      Its: President
                                          ------------------------------

                                      Name: Gail K. Naughton, Ph.D.
                                           -----------------------------

                              Address: 10933 North Torrey Pines Road
                                      ---------------------------------
                                       La Jolla, CA  92037
                                      ---------------------------------



                                      13.