Paul Klee was one of the most important fine artists of the 20th century. His paintings, graphics and writings were influenced by Expressionism, Constructivism, Cubism, Primitivism and Surrealism. Thanks to Wassily Kandinsky, his works were included in the second exhibition of the group 'Der Blaue Reiter' in 1912. That same year, Klee visited Robert Delaunay in Paris, whose latest 'window pictures' greatly impressed him on account of their colourful abstraction. But only a trip to Tunis with August Macke and Louis Moilliet made him turn to painting for good. After World War I, Klee lectured at the Bauhaus in Weimar, and later in Dessau. There, he developed his professed aim: to make visible the mysterious intermediate realm between the real appearance and the essence of things. After having been a professor at the Düsseldorf Art Academy for a short while, Klee was banned from teaching in 1933 and emigrated to Switzerland. There, ravaged by disease, he developed his extensive late work in which representations of angels became a central theme.