This comprehensive book focuses on Thomas Ruff's photographic series from the past twenty years. These series are based on found photographs from a variety of sources. The source materials range from early nineteenth century photography to machine-made photographs of distant planets, from post-war press photos to propaganda images from the People's Republic of China, and from Internet pornography to computer generated photograms. In each series, Ruff explores the historical and technical conditions of photography by examining these highly varied pictorial worlds. At the same time, he takes into consideration the afterlife of the images in archives, databases and on the Internet, thus formulating highly complex perspectives on the photographic medium and the world that has already been photographed. The catalogue was published in conjunction with the exhibition at the K20 Kunstsammlung Nordrhein-Westfalen in Düsseldorf.