Picture libraries exist in many shapes and sizes, within the broad categories of public collections, private and usually specialised collections, and photoagencies. Users of picture libraries range from students to professional picture researchers, though even the latter may need guidance. The picture librarian combines the roles of collectors and custodian while also making the collection available for use. The Mary Evans Picture Library, which comprises some two million prints mounted and filed under subject headings, provides ‘visual documentation of the past’ up to the late 1920s, with an emphasis on social conditions. Cross-references and photographic duplicates (retained for permanent reference) are interfiled with the prints, most of which are available for loan and any of which may be copied. The organisation of the library corresponds to its users’ needs rather than to a rigid system.