Leonardo's greatest triumph was the smile of the Mona Lisa, which he started working on in 1503 and continued laboring over nearly until his death 16 years later. His distinctive approach was to apply the glaze in extraordinarily thin strokes and then very slowly, over months and years, apply additional layer upon thin layer. The result is a masterpiece that invites and responds to human interactions--a smile that seems to react to our gaze.

As an engineer, da Vinci conceived ideas vastly ahead of his time, conceptually inventing the parachute, the helicopter, an armored fighting vehicle, the use of concentrated solar power, a calculator, a rudimentary theory of plate tectonics, and the double hull.

In 1652, while installing a doorway in the wall that holds The Last Supper, builders cut into the bottom-center of the mural, lopping off Jesus' feet. While it may seem like a minor loss, many historians believe (based on examination of early copies) that Jesus' feet were in a position symbolizing the forthcoming crucifixion.

When Leonardo was a very young man, a local peasant made himself a round shield and requested that da Vinci's father have it painted for him. Leonardo, inspired by the story of Medusa, responded with a painting of a monster spitting fire that was so terrifying that his father bought a different shield to give to the peasant and sold Leonardo's to a Florentine art dealer for 100 ducats, who in turn sold it to the Duke of Milan.

When the Mona Lisa was stolen from the Louvre in 1911, it caused a media sensation, and visitors queued for hours to see the vacant wall. The empty space it left behind actually attracted more visitors than the painting had!

As a successful artist, Leonardo was given permission to dissect human corpses at the Hospital of Santa Maria Nuova in Florence and later at hospitals in Milan and Rome. He also dissected cows, birds, monkeys, bears, and frogs, comparing their anatomical structure with that of humans.

By the age of 17, he had became an apprentice in the workshop of Andrea del Verrocchio, who was the leading Florentine painter and sculptor of his day. This was about the time of the death of Verrocchio's master, the great sculptor Donatello. Other famous painters apprenticed in the workshop or associated with it include Ghirlandaio, Perugino, Botticelli, and Lorenzo di Credi.

Leonardo's aspirations were temporarily derailed when he and three other young men were charged with the crime of sodomy, a serious accusation that could have led to his execution. Leonardo, 24, was acquitted, but in the aftermath he disappeared for two years. He reemerged in 1478 to accept a commission at a chapel in Florence.

He often wrote in mirror script, reversing his handwriting so that it could only be read if the page was held up to a mirror. Despite some suspicion that he was trying to be secretive, the truth is less sensational--as a left-handed writer, he could avoid smearing the ink by writing in reverse.

Being frequently visited by Francis, he drew plans for an immense castle town the king intended to erect at Romorantin, and made a mechanical lion, which during a pageant walked toward the king and--upon being struck by a wand--opened its chest to reveal a cluster of lilies.