Between 1943 and 1952, Jackson Pollock created patterns by dripping paint onto horizontal canvases. In 1999 the authors identified the patterns as fractal. Ending 50 years of debate over the content of his paintings, the results raised the more general question of how a human being could create fractals. The authors, by analyzing film that recorded the evolution of Pollock's patterns as a function of time, show that the fractals resulted from a systematic construction process involving multiple layers of painted patterns. These results are interpreted within the context of recent visual perception studies of fractal patterns.