Cézanne's explorations of geometric simplification and optical phenomena inspired Picasso, Braque, Metzinger, Gleizes, Gris and others to experiment with ever more complex views of the same subject and eventually to the fracturing of form. Cézanne thus sparked one of the most revolutionary areas of artistic enquiry of the 20th century, one which was to affect profoundly the development of modern art. Picasso referred to Cézanne as "the father of us all" and claimed him as "my one and only master!" Other painters such as Edgar Degas, Pierre-Auguste Renoir, Paul Gauguin, Kasimir Malevich, Georges Rouault, Paul Klee, and Henri Matisse acknowledged Cézanne's genius.