Jan Steven van Calcar (Italian: Giovanni da Calcar, Latin: Ioannes Stephanus Calcarensis) (c. 1499–1546) was a German-born Italian painter.
He is the one who made the illustrations for "De humani corporis fabrica libri septem" (On the Fabric of the Human Body in Seven Books), the famous anatomy treatise written by Andreas Vesalius in 1543, which had an extraordinary influence on the painting and sculpture that followed.
But that's not why I'm introducing him to you, but because he's very nice to me, he looks like Till Eulenspiegel :)