The Thesaurus for Graphic Materials is a tool for indexing visual materials by subject and genre/format. The thesaurus includes more than 7,000 subject terms to index topic shown or reflected in pictures, and 650 genre/format terms to index types of photographs, prints, design drawings, ephemera and other categories. New terms are added regularly. TGM is searchable through the Prints and Photographs Online Catalog (PPOC).