Can science be used to further our understanding of art? This question meets with reservations from both scientists and artists. However, for the abstract paintings produced by Jackson Pollock in the 1940s and 1950s, scientific objectivity proves to be an essential tool for determining their fundamental content. Pollock dripped paint from a can onto vast canvases on the floor of his barn. Although recognized as a crucial advance in the evolution of modern art, the precise quality and significance of the patterns created by this unorthodox technique remain controversial. Here we analyse Pollock's patterns and show that they are fractal. In other words, they display the fingerprint of nature. In contrast to the broken lines painted by conventional brush strokes on canvas, Pollock used a constant stream of paint to produce a uniquely continuous trajectory as it splattered onto the canvas below. A typical canvas would be reworked many times over a period of several months, with Pollock building up a dense web of paint trajectories. This repetitive and cumulative process -sometimes called "continuous dynamic" painting- is strikingly similar to the way in which patterns evolve in nature.    more »