The Warburg Institute is concerned mainly with cultural history, art history and history of ideas, especially in the Renaissance. It aims to promote and conduct research on the interaction of cultures, using verbal and visual materials. It specializes in the influence of ancient Mediterranean traditions on European culture from the Middle Ages to the modern period. Its open–access library has outstanding strengths in Byzantine, Medieval and Renaissance art, Arabic, Medieval and Renaissance philosophy, the history of religion, science and magic, Italian history, the history of the classical tradition, and humanism. In several of these fields it can claim to be the most important library in the world. The photographic collection, organised by subject, documents the iconographical traditions of western art and facilitates research into these traditions as well as the identification of the subject of individual images. The archive holds the papers of Aby Warburg, Fritz Saxl and other staff members of the Institute, including both sides of their correspondence with many leading scholars of the twentieth century.