UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

SCHEDULE 13D

Item 1.

Security and Issuer

This Amendment No. 3 to the Schedule 13D amends and supplements the Schedule 13D, as amended by Amendment No. 5 to the Tender Offer Statement on Schedule TO filed on October 8, 2010 and by Amendment No. 2 to the Schedule 13D filed on October 15, 2010 and as may be further amended from time to time (the “Schedule 13D”), originally filed on August 29, 2010 by 3M Company and its wholly-owned subsidiary Ventura Acquisition Corporation (collectively, the “Reporting Persons”) with respect to the common stock, par value $0.001 per share (the “Shares”), of Cogent, Inc. (“Cogent” or the “Issuer”).

Unless otherwise indicated, all capitalized terms used herein but not defined herein shall have the same meaning as set forth in the Schedule 13D.

Item 4.

Purpose of the Transaction

Item 4 of the Schedule 13D is hereby amended, in pertinent part, as follows:

Pursuant to the Merger Agreement, 3M was entitled, upon payment for Shares tendered pursuant to the Offer, to designate a number of directors of Cogent, rounded up to the next whole number, that is equal to the product of the total number of directors on the Cogent board and the percentage that the number of common shares owned by Purchaser or any other subsidiary of 3M bears to the total number of common shares outstanding.  Accordingly, on October 21, 2010, 3M’s designees, Michael P. Delkoski, Carol. A. Peterson, Rudy Pitera, Maureen C. Faricy and Kimberly Torseth, were appointed to the Cogent board.

Item 5.

Interest in Securities of the Issuer

Item 5 of the Schedule 13D is hereby amended, in pertinent part, as follows:

(a) — (b) The Reporting Persons have acquired 13,441,686 additional Shares in the subsequent offering period that commenced October 8, 2010.  Based on information provided by the Issuer, the Reporting Persons are the beneficial owners of an aggregate of 59,823,465 Shares, representing approximately 67.6% of the outstanding Shares as of October 8, 2010.  The information set forth in Item 4 is incorporated herein by reference.

Additional Information

This document is neither an offer to purchase nor a solicitation of an offer to sell shares of Cogent, Inc.  3M Company and Ventura Acquisition Corporation have filed a Tender Offer Statement on Schedule TO containing an offer to purchase, forms of letters of transmittal and other documents relating to the tender offer and Cogent, Inc. has filed a Solicitation/Recommendation Statement on Schedule 14D-9 with respect to the tender offer.  3M Company, Ventura Acquisition Corporation and Cogent, Inc. have mailed these documents to the stockholders of Cogent, Inc.  These documents contain important information about the tender offer and stockholders of Cogent, Inc. are urged to read them carefully. Copies of these documents and other documents filed by Cogent, Inc., 3M Company or Ventura Acquisition Corporation are available for free on the website maintained by the SEC at www.sec.gov.  In addition, a free copy of these documents may also be obtained from the information agent, Georgeson Inc., 199 Water Street, 26th Floor, New York, NY 10038, by calling toll free (866) 647-8872 or, for bankers and brokers, (212) 440-9800.

Dated:    October 22, 2010

3M Company

By:

/s/ Gregg M. Larson

Name: Gregg M. Larson

Title: Deputy General Counsel and Secretary

Ventura Acquisition Corporation

By:

/s/ Carol A. Peterson

Name: Carol A. Peterson

Title: Secretary