UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

OMB APPROVAL

Washington, DC 20549

OMB Number: 3235-0145

Expires: February 28, 2009

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x

Rule 13d-1(b)

o

Rule 13d-1(c)

o

Rule 13d-1(d)

CUSIP No. 630077105

1.

Names of Reporting Persons
I.R.S. IDENTIFICATION NO. OF ABOVE PERSONS (ENTITIES ONLY)
The TCW Group, Inc., on behalf of the TCW Business Unit

2.

Check the Appropriate Box if a Member of a Group*

(a)

o

(b)

x

3.

SEC Use Only

4.

Citizenship or Place of Organization
Nevada corporation

Number of
Shares
Beneficially
Owned by
Each
Reporting
Person With

5.

Sole Voting Power
-0-

6.

Shared Voting Power
28,921

7.

Sole Dispositive Power
-0-

8.

Shared Dispositive Power
28,921

9.

Aggregate Amount Beneficially Owned by Each Reporting Person
28,921

10.

Check Box if the Aggregate Amount in Row (9) Excludes Certain Shares*  o

11.

Percent of Class Represented by Amount in Row (9)
0.2%(see response to Item 4)

12.

Type of Reporting Person*(See Instructions)
HC/CO

Item 1

(a).

Name of Issuer:
Nanometrics Incorporated

Item 1

(b).

Address of Issuer’s Principal Executive Offices:
1550 Buckeye Drive

Milpitas, CA 95035

Item 2

(a).

Name of Persons Filing:

Item 2

(b).

Address of Principal Business Office, or if none, Residence:

Item 2

(c).

Citizenship:
The TCW Group, Inc., on behalf of the TCW Business Unit

865 South Figueroa Street

Los Angeles, CA 90017

(Nevada Corporation)

Item 2

(d).

Title of Class of Securities:
Common Stock

Item 2

(e).

CUSIP Number:
630077105

Item 3.

If This Statement Is Filed Pursuant to §§240.13d-1(b), or 240.13d-2(b) or (c), Check Whether the Person Filing is a:

(a)

o

Broker or dealer registered under section 15 of the Exchange  Act (15 U.S.C. 78o).

(b)

o

Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c)

o

Insurance company as defined in section 3(a)(19) of the Exchange Act (15 U.S.C. 78c).

(d)

o

Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8).

(e)

o

An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E).

(f)

o

An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F).

(g)

x

A parent holding company or control person in accordance with §240.13d-1(b)(1)(ii)(G).

(see Item 7)

The TCW Group, Inc., on behalf of the TCW Business Unit

(h)

o

A savings association as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i)

o

A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j)

o

Group, in accordance with §240.13d-1(b)(1)(ii)(J).

If this statement is filed pursuant to Rule 13d-1(c), check this box. o

Item 4.

Ownership **

The TCW Group, Inc., on behalf of the Business Unit ***

(a)

Amount beneficially owned:   

28,921

(b)

Percent of class:   

0.2%

(c)

Number of shares as to which such person has:

(i)

Sole power to vote or to direct the vote:

none.

(ii)

Shared power to vote or to direct the vote:

28,921

(iii)

Sole power to dispose or to direct the disposition of:

none.

(iv)

Shared power to dispose or to direct the disposition of:

28,921

Item 5.

Ownership of Five Percent or Less of a Class.

If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following   x.

Item 6.

Ownership of More than Five Percent on Behalf of Another Person.

Not Applicable.

Item 7.

Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company.

See Exhibit A.

Item 8.

Identification and Classification of Members of the Group.

Not applicable.  See Exhibit A.

Item 9.

Notice of Dissolution of Group.

Not applicable.

Item 10.

Certification.

Because this statement is filed pursuant to Rule 13d-1(b), the following certification is included:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.

The TCW Group, Inc., on behalf of the
TCW Business Unit

By:

/s/ Linda D. Barker

Linda D. Barker

Authorized Signatory