Cubism was a revolutionary new approach to visual representation invented in 1907–08 by Pablo Picasso and Georges Braque. In Cubist paintings and collages, motifs are fragmented and re-assembled, with multiple views coexisting within the same picture. This marked a radical break from the European tradition of creating a consistent spatial illusion from a fixed viewpoint. In addition to Picasso and Braque, early practitioners of Cubism included Fernand Léger, Juan Gris, Robert and Sonia Delaunay, and Jean Metzinger. Web resource here.
Juan Gris. The Smoker (Frank Haviland). Oil on canvas. 1913. Museo Nacional Thyssen-Bornemisza, Madrid.