There are two main types of cubism, analytical cubism and synthetic cubism. Analytic cubism was mainly practiced by Braque, and is very simple, with dark, almost monochromatic colours. Synthetic cubism was much more energetic, and often made use of collage including the use of several two-dimensional materials. This type of cubism was developed by Picasso. During the two artists' time of collaboration from 1907 and ending with the First World War, their styles intermingled and they painted the same subjects, making their works at times closely resemble each other.