Artists' letters form one of the richest areas of the Getty Research Institute's archival collections. Frequently illustrated, their diversity of information—ranging from business dealings with gallerists and patrons, to artistic struggles and intimate details of friendships and lovers—makes them an essential resource for scholars, all the more so in that many remain unpublished. The collection reaches back to the Renaissance—a notable example is Bartolomeo Ammanati's letter concerning his Neptune fountain in Florence—and continues forward, with a growing quantity of correspondence from contemporary artists writing from around the world. The richest holdings are from European artists of the 19th and 20th centuries, such as Marcel Duchamp, Paul Gauguin, Jean-Léon Gérôme, Wassily Kandinsky, F. T. Marinetti, Henri Matisse, Claude Monet, Albert Renger-Patzsch, and Paul Signac. In the latter half of the 20th century, Ay-O, Jess Collins, Bruce Conner, Jay de Feo, Dick Higgins, David Hockney, and Yvonne Rainer are but a few of the artists included.