Art by Leonardo da Vinci

Leonardo finished remarkably few paintings, most estimates land somewhere between 15 and 20 in his entire lifetime, which is a strange fact to sit with given how completely he's come to define what a Renaissance genius is supposed to look like. He was notorious among his own patrons for starting commissions and never delivering them, partly because his curiosity kept pulling him sideways into anatomy, hydraulics, flight, and military engineering, and partly because he was, by his own account, never quite satisfied that a painting was actually finished.

His notebooks are where most of that restlessness ended up: thousands of pages of mirror-written notes (he was left-handed, and historians still debate whether it was habit or a kind of privacy), covering everything from the mechanics of muscle and tendon to designs for machines that wouldn't exist for centuries. He wasn't writing for an audience. Almost none of it was published in his lifetime.

The Mona Lisa took him roughly 16 years, on and off, and he reportedly never delivered it to whoever originally commissioned it. He kept it with him instead, still working on it, until he died in France under the patronage of King Francis I. In 2017, a painting attributed to him, Salvator Mundi, sold at auction for $450.3 million, the highest price ever paid for a painting, though a meaningful number of scholars still dispute how much of it, if any, is actually by his hand.