Throughout the twentieth century the medium of drawing was repeatedly redefined. The contributions to art history made by Ernst Ludwig Kirchner, Francis Picabia, Roy Lichtenstein, Henri Michaux, and sculptor David Smith defined the art of drawing. Drawing was further explored and expanded by many later artists, including a number from the Düsseldorf Academy, for example Anzinger Siegfried, Joseph Beuys, Anthony Cragg, Jörg Immendorff, Konrad Klapheck, AR Penck, Gerhard Richter, Rosemarie Trockel