1480s. His drawings of a fetus in utero, the heart and vascular system, sex organs and other bone and muscular structures are some of the first on human record.

In addition to his anatomical investigations, da Vinci studied botany, geology, zoology, hydraulics, aeronautics and physics. He sketched his observations on loose sheets of papers and pads that he tucked inside his belt.

Da Vinci placed the papers in notebooks and arranged them around four broad themes—painting, architecture, mechanics and human anatomy. He filled dozens of notebooks with finely drawn illustrations and scientific observations.

Sculptures

Ludovico Sforza also tasked da Vinci with sculpting a 16-foot-tall bronze equestrian statue of his father and founder of the family dynasty, Francesco Sforza. With the help of apprentices and students in his workshop, da Vinci worked onthe project on and off for more than a dozen years.

Da Vinci sculpted a life-size clay model of the statue, but the project was put on hold when war with France required bronze to be used for casting cannons, not sculptures. After French forces overran Milan in 1499 — and shot the clay model to pieces — da Vinci fled the city along with the duke and the Sforza family.

Ironically, Gian Giacomo Trivulzio, who led the French forces that conquered Ludovico in 1499, followed in his foe’s footsteps and commissioned da Vinci to sculpt a grand equestrian statue, one that could be mounted on his tomb. After years of work and numerous sketches by da Vinci, Trivulzio decided to scale back the size of the statue, which was