Since the 1940s Gianni Mattioli's collection of modern art has been a touchstone of the history of twentieth century collecting, both for the quality of its masterpieces (Boccioni's Materia, Balla's Mercury Passing Before the Sun, de Chirico's The Disquieting Muses, and Modigliani's Red Nude for example) and for its underlying program. Mattioli was guided by the double purpose of representing the major movements of modern Italian art (including the retrieval of Futurism and Metaphysical painting from their critical oblivion) and of presenting them coherently to the public, with an awareness of the civilizing effect of living art on contemporary society. This major new contribution to our knowledge of Italian modern art is the catalogue of twenty-six works in Mattioli's collection, dating from 1910 to 1921, that together have been listed under Italian law no. 1089 of June 1, 1939 for the protection of the cultural heritage and which were deposited in 1997 at the Peggy Guggenheim Collection, Venice. Each painting is studied in an essay that explores its origins and iconography, its relation to Italian and international pictorial sources, its position in contemporary aesthetic debate, and its critical history. In several cases infrared reflectography has revealed new information about the artist's methods. Each essay presents valuable insights and facts about the leading artists in the period of Italy's maximum engagement with the European avant-garde. The book opens with a biographical essay by Laura Mattioli Rossi, the collector's daughter, which describes the network of opportunities, connections and strategies that brought the collection together. The essay is enriched by approximately one hundred unpublished documents, making it possible for the first time to analyze the mechanism of prices, market trends and the role of galleries of that time.