During the late 19th and early 20th centuries, Europeans were discovering African, Polynesian, Micronesian and Native American art. Artists such as Paul Gauguin, Henri Matisse, and Pablo Picasso were intrigued and inspired by the stark power and simplicity of styles of those foreign cultures. Around 1906, Picasso met Matisse through Gertrude Stein, at a time when both artists had recently acquired an interest in primitivism, Iberian sculpture, African art and African tribal masks. They became friendly rivals and competed with each other throughout their careers, perhaps leading to Picasso entering a new period in his work by 1907, marked by the influence of Greek, Iberian and African art. Picasso's paintings of 1907 have been characterized as Protocubism, as notably seen in Les Demoiselles d'Avignon, the antecedent of Cubism.