For nearly 80 of his 91 years, Picasso devoted himself to an artistic production that contributed significantly to the whole development of modern art in the 20th century, notably through the invention of Cubism (with the artist Georges Braque) about 1907. Building on the work of 19th-century art movements, Cubism radically changed the course of representation by acknowledging the illusionistic tricks required to depict three-dimensional objects on a flat canvas. In rejecting the naturalism that Western artists had favoured since the Renaissance, Cubism consequently changed the ways in which people think about the role of art. It ushered in the abstract movements of the 20th century and continues to influence the art of the 21st. Picasso never kept within stylistic boundaries, and he continued to experiment with different approaches and media into the last decade of his life.