Via Rhizome.org:

In 1955, French director, Henri-Georges Clouzot had the most amazing idea. He would film Pablo Picasso as he painted 20 artworks, ranging from quick sketches to widescreen color oil paintings.

Time-lapse video of Picasso making a painting, from start to finish

It’s amazing to watch this, and watch the painting develop, along with the ideas.  Pay attention to the bull, and how it changes from a more literal one to a cubist one over the course of the painting.