It's not clear when Leonardo da Vinci's fascination with the human body began, but some of his earliest anatomical drawings date back to his time in Milan during the 1480s, according to BBC. It all started with the sketch of a human skull and ended with a collection of anatomical manuscripts that contain over 240 drawings and a small book's worth of notes, and within those notes, da Vinci admits to dissecting more than 30 bodies.

Da Vinci kept his early studies in human anatomy constrained to the musculoskeletal system. According to Britannica, he believed an artist needed to understand these structures best because they formed the basis for all portraits. First bones, then muscles, then the exterior. Bones are, after all, the base of the human figure. Later in life, near the end of the 15th century, the maestro would make anatomy its own subject of study while working alongside a professor at the University of Pavia. The professor did the dissecting until his unexpected death, then da Vinci assumed both the cutting and the sketching tasks.

His studies provided a lot of "firsts." Da Vinci, according to BBC, was one of (if not the) first to discover that the heart had four chambers. His drawings also birthed the field of anatomical art, also called "medical illustration," and, according to MedicineNet, he devised a technique to fill the heart and blood vessels with wax to preserve their integrity, a technique still used in these modern times.

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