Cubism was an art movement which began in the early 20th century. The main artists were Pablo Picasso and George Braque. Picasso was inspired by the work of Henri Matisse and they were both interested in African art.

Picasso's painting, Demoiselles D'Avignan is thought to be the starting point of Cubism. Picasso had painted in a whole new style. 

Demoiselles D'Avignon.

Some people say that Cezanne also had the roots of Cubism in his work. He broke the surfaces of painting to show different viewpoints.
                                     
                                                                                                                                                                          Quarry Bibemus
                                                                                                                                                                            Paul Cezanne

Picasso and Braque worked together from 1908 until the first World War began in 1914. The term "Cubism" was first used by a French art critic called Louis Vauxcelles after he saw one of Braques paintings, he had described it as being full of little cubes.