In 1912, Picasso incorporated a piece of chair caning into one of his works. While this act seems tame today, it was quite radical at the time, when the idea of art necessitated a removal from the everyday world. By bridging the divide between paint and reality, Picasso helped to bring on an era of radical change in art, when rules were thrown out and materials of all kinds began to be seen as capable of becoming art.
Five years later, in 1917, Marcel Duchamp exhibited a urinal in an art show. Whether he was trying to make the point that everything is art, or that nothing is art, has been the subject of discussion ever since. Duchamp's discovery of the "readymade," as he called the urinal and other objects that he chose, erased the line between art and life even more thoroughly than Picasso had done.
In the 1920s, members of the Dada movement incorporated newspapers, detritus off the street, bits of wood, dressmakers' dummies and many other objects in their artwork. Although Dada was a self-proclaimed anti-art movement, their continuation of Picasso's and Duchamp's use of "non-art" objects within an artistic context helped to promote the creation of mixed-media art, resulting in the continuation, rather than the destruction, of art.
In the 1950s, Arman became very successful as an artist primarily by assembling large numbers of objects in one place. His signature style was a collection of objects--such as wrenches, cutlery or shoes--contained within a plexiglass box. Many have interpreted his art as either a condemnation or a celebration of mass consumption, the true beauty of it being that it could be either.
In the 1960s, Jean Tinguely built sculptures out of bits of steel and other metals, found objects and gears. The distinguishing feature of Tinguely's creations was that they were animated and self-destroying. When Tinguely had completed a work, he would organize a performance to which hundreds of people would come and watch his chaotic creations smash themselves into oblivion.