Picasso continued to study and absorb these exciting experiments in the art around him. In the summer of 1906, vacationing with Fernande in a Catalan village, Picasso began carving wooden sculptures. In these works, Picasso was driven to a simplification of form by both the technical properties of the wood he worked with and by the compelling memory of the prehistoric Spanish sculpture he had seen in the Louvre. His experience in wood-carving led to changes in his painting; his portrait of Gertrude Stein–in which he so radically simplified her face that it became the image of a chiseled mask, perfectly opaque and yet expressive–marks a crucial shift in his painting. He stopped painting what he saw and started painting what he thought. Stein liked the portrait very much.
At the beginning of 1907, Picasso began a painting, "Les Demoiselles d'Avignon" ("The Young Women of Avignon"), that would become arguably the most important of the century. The painting began as a narrative brothel scene, with five prostitutes and two men–a medical student and a sailor. But the painting metamorphosed as he worked on it; Picasso painted over the clients, leaving the five women to gaze out at the viewer, their faces terrifyingly bold and solicitous. There is a strong undercurrent of sexual anxiety. The features of the three women to the left were inspired by the prehistoric sculpture that had interested him in the summer; those of the two to the right were based on the masks that Picasso saw in the African and Oceanic collections in the Musée d'Ethnographie du Trocadéro in Paris. While no specific African or Pacific sources have been identified, Picasso was deeply impressed by what he saw in these collections, and they were to be one of his primary influences for the next several years. Art historians once classified this phase of Picasso's work as his "Negro Period." French imperialism in Africa and the Pacific was at its high point, and gunboats and trading steamers brought back ritual carvings and masks as curiosities. While the African carvings, which Picasso owned, had a kind of dignified aloofness, he, like other Europeans of his time, viewed Africa as the symbol of savagery. Unlike most Europeans, however, Picasso saw this savagery as a source of vitality and renewal that he wanted to incorporate for himself and for European painting. His interpretation of African art, in these mask-like faces, was based on this idea of African savagery; his brush-strokes are hacking, impetuous, and violent.
"Les Demoiselles" was so shockingly new that Gertrude Stein called it "a veritable cataclysm." She meant this, of course, as a compliment. Not only did this painting later become a turning point duly remarked upon in every history of modern art, but Picasso felt at the time that his whole understanding of painting was revised in the course of this canvas' creation. He called it his "first exorcism picture."