"The inventors of Cubism, Georges Braque and Pablo Picasso, replaced perspective with a new kind of pictorial space: instead of receding into the distance, their paintings seemed to advance toward the viewer in a series of overlapping planes. In 1911 they supplemented representation with simulation, adding stenciled letters and patches of wood-graining to their paintings. In 1912 they glued actual strips of newspaper, wallpaper, and other materials to the surfaces. Their colleague Juan Gris went a step further and inserted old engravings, creating pictures within pictures. The heroic story of how Braque, Picasso, and Gris invented a new pictorial space and a new medium—collage—is a staple of textbooks and introductory courses on art history."