While in Milan, Leonardo da Vinci came up with his idea and began plotting the Treatise on Anatomy. In Milan Leonardo met the anatomist Marcantonio della Torre, a proffessor at the Pavia Medical school. One of the most important discoveries of Leonardo in Milan was Leonardo's advancements in embryology. On a cadaver Leonardo was able to expose a human fetus which allowed him to make many discoveries. He correctly identified the position of the fetus and discovered a variety of things about the placenta. Leonardo was unable to finish his treaty on anatomy, as in 1511 Marcantonio della Torre died of the plague. 

Works cited

Norman, Jeremy. “Leonardo's Anatomical Drawings.” Leonardo's Anatomical Drawings : History of Information, Jeremy Norman & Co., Inc, 2020, Retreived from www.historyofinformation.com/detail.php?entryid=2254.

Gilson, Hilary. "Leonardo da Vinci's Embryological Drawings of the Fetus". Embryo Project Encyclopedia (2008-08-19). ISSN: 1940-5030, Retreived from http://embryo.asu.edu/handle/10776/1929.