Leonardo has long been recognised as one of the great artists of the Renaissance, but he was also a pioneer in the understanding of human anatomy. He intended to publish his ground-breaking work in a treatise on anatomy, and had he done so his discoveries would have transformed European knowledge of the subject. But on Leonardo's death in 1519 the drawings remained a mass of undigested material among his private papers and their significance was effectively lost to the world for almost 400 years.