Rudolf Bauer (1889–1953) was a pioneering German abstract artist closely linked to the Der Sturm movement in Berlin, where he exhibited alongside artists such as Wassily Kandinsky, Paul Klee, and Franz Marc. A key figure in the development of non-objective art, Bauer explored the expressive potential of color and form to evoke spiritual and emotional states. Together with his close friends Hilla von Rebay and Otto Nebel, he co-founded Die Krater, an avant-garde group dedicated to the pursuit of pure abstraction. His friendship with von Rebay—whom this work honors—was central to his artistic journey and to the early vision that later inspired the Guggenheim collection.