From the Bureau of Engraving and Printing website (http://www.bep.treas.gov):

The Bureau manufactures the financial and other securities of the United States. Accordingly, the Bureau designs, prints, and furnishes a large variety of security products, including Federal Reserve notes, most U.S. postage stamps, Treasury securities, identification cards, naturalization certificates, and other special security documents. All products are designed and manufactured with advanced counterfeit deterrence features to ensure product integrity, and the Bureau advises other Federal agencies on document security matters. The Bureau also processes claims for the redemption of mutilated currency. The Bureau's research and development efforts focus on the continued use of automation in the production process and counterfeit deterrent technologies for use in security documents, especially U.S. currency.