Pablo Ruiz y Picasso, known as Pablo Picasso (1881 –1973) was a Spanish painter, sculptor, printmaker, ceramicist, and stage designer who spent most of his adult life in France. As one of the greatest and most influential artists of the 20th century, he is widely known for co-founding the Cubist movement, the invention of constructed sculpture, the co-invention of collage, and for the wide variety of styles that he helped develop and explore. Among his most famous works are the proto-Cubist Les Demoiselles d'Avignon (1907), and Guernica (1937), a portrayal of the German bombing of Guernica during the Spanish Civil War. Picasso, Henri Matisse and Marcel Duchamp are commonly regarded as the three artists who most defined the revolutionary developments in the plastic arts in the opening decades of the 20th century, responsible for significant developments in painting, sculpture, printmaking and ceramics. Picasso demonstrated extraordinary artistic talent in his early years, painting in a realistic manner through his childhood and adolescence. During the first decade of the 20th century, his style changed as he experimented with different theories, techniques, and ideas. His revolutionary artistic accomplishments brought him universal renown and immense fortune, making him one of the best-known figures in 20th-century art. Prolific as a draftsman, sculptor, and printmaker, Picasso's primary medium was painting. He usually painted from imagination or memory, and worked in many different styles throughout his career. Although he used color as an expressive element, he relied on drawing rather than subtleties of color to create form and space. A nanoprobe of Picasso's The Red Armchair (1931) by physicists at Argonne National Laboratory in 2012 confirmed art historians' belief that Picasso used common house paint in many of his paintings. Picasso’s work is often categorized into periods. While the names of many of his later periods are debated, the most commonly accepted periods in his work are the Blue Period (1901–1904), the Rose Period (1905–1907), the African-influenced Period (1908–1909), Analytic Cubism (1909–1912), and Synthetic Cubism (1912–1919). In 1939–40 the Museum of Modern Art in New York City, under its director Alfred Barr, a Picasso enthusiast, held a major and highly successful retrospective of his principal works up until that time. This exhibition lionized the artist, brought into full public view in America the scope of his artistry, and resulted in a reinterpretation of his work by contemporary art historians and scholars. Picasso was exceptionally prolific throughout his long lifetime. The total number of artworks he produced has been estimated at 50,000, comprising 1,885 paintings; 1,228 sculptures; 2,880 ceramics, roughly 12,000 drawings, many thousands of prints, and numerous tapestries and rugs.