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                                                                  EXHIBIT 10.9.1

                    FIRST AMENDMENT TO DEVELOPMENT AGREEMENT

Nanosys Inc. ("Nanosys"), and Matsushita Electric Works, Ltd. ("MEW") are
parties to a certain Development Agreement ("the Agreement") dated and effective
as of November 18th, 2002 ("the Effective Date"). This First Amendment to the
Agreement is entered into and effective as of February 8, 2004 ("the First
Amendment Date").

WHEREAS, MEW and Nanosys wish to extend the Development Period of the Agreement;

NOW, THEREFORE, in consideration of the foregoing premises and the mutual
covenants herein contained, the parties hereby agree to amend the Agreement as
follows:

A.       Section 1.5 of the Agreement is hereby deleted and replaced with the
         following:

         1.5      "Development Period" shall mean the period commencing upon
                  Nanosys' receipt of the Two Million United States Dollars
                  ($2,000,000) payment set forth in Section 3.1, and unless'
                  terminated earlier upon termination of this Agreement pursuant
                  to Article 6 or extended by mutual written agreement of the
                  parties, expiring twenty one (21) months after the Effective
                  Date.

B.       In Section 3.1 of the Agreement, the third sentence which states in
         its entirety

         "As additional consideration, within thirty (30) days of the conclusion
         of the Development Period, provided that Nanosys has met its
         Development Goals or MEW provides or has provided Nanosys with an
         Exercise Notice pursuant to Section 3.2 or MEW elects in its discretion
         to make such payment, MEW shall pay Nanosys an additional Five Hundred
         Thousand United States Dollars (U.S. $500,000)."

is hereby deleted.

C.       In Section 3.5 of the Agreement, the opening clause that states in its
         entirety:

         "Option to License Phase I Technology. Provided that MEW has made the
         Five Hundred Thousand Dollars ($500,000) payment to Nanosys pursuant to
         Section 3.1,"

is hereby deleted and replaced with the following:

         "Option to License Phase I Technology. Provided that MEW has provided
         Nanosys with the Exercise Notice pursuant to Section 3.2,"

D.       In consideration of the foregoing amendments, MEW shall pay to Nanosys
the amount of Five Hundred Thousand United States Dollars ($500,000) ("Amendment
Fee") within thirty (30) days of the First Amendment Date. Such payment shall be
made in accordance with the terms respecting payment as set forth in the Article
3 of the Agreement.


E.       Unless expressly amended herein or by subsequent amendments agreed to
by the parties in a signed written amendment, all other terms of the Agreement,
including but not limited to terms related to interpretation and enforcement of
the Agreement, shall remain in full force and effect as originally agreed to in
the Agreement, and shall apply equally to the terms of this First Amendment. The
parties hereby expressly reaffirm their obligations under the Agreement,
including their obligation to prepare and provide a Final Report upon expiration
of the Development Period (as amended), and the parties acknowledge that any
delay in the delivery of such Final Report will result in a corresponding
extension of the time periods measured by reference to the Final Report,
including the Election Period.


*** Confidential treatment requested pursuant to a request for confidential
treatment filed with the Securities and Exchange Commission. Omitted portions
have been filed separately with the Commission.

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IN WITNESS WHEREOF, the parties through their duly authorized representatives
have executed this First Amendment as of the date last set forth below

NANOSYS, INC.                             MATSUSHITA ELECTRIC WORKS, LTD.

By:  /s/ Calvin Chow                       By:  /s/ Hiroshi Kikuchi
     ----------------------------               --------------------------------
Name: Calvin Chow                          Name: Hiroshi Kikuchi
Title: Chief Executive Officer             Title: Executive Vice President
Date: 2-17-04                              Date: February 17, 2004

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