It was at Padua that he developed his study of anatomy, the fruits of which were published most completely in De humani corporis fabrica (known as the Fabrica) of 1543, in which he provided a fuller description of the human body than had ever been achieved before (O'Malley, p.112; Nutton, 'The Man'). In the process he was able to show that the ancient Graeco-Roman medical writer Galen (131-201 CE), who was still relied on as the principal authority on the subject, had in fact made many errors; in particular he reminded his readers that Galen had derived a large part of his anatomy from the study of animals, especially monkeys.

One of the keys to Vesalius' success was the fact that he combined an extraordinary knowledge of medicine with remarkable practical skill in dissecting bodies. His book combined very detailed written exposition with an elaborate apparatus of illustrations; his descriptions were thus supported by visual demonstration in a manner that was brilliantly effective in conveying his observations.