Sixty-six million years ago, an asteroid wiped out the dinosaurs in a fiery global catastrophe. But we know little about how their successors, the mammals, recovered and took over the world. Now, hidden inside ordinary-looking rocks, an astonishing trove of fossils reveals a dramatic new picture of how rat-sized creatures ballooned in size and began to evolve into the vast array of species—from cheetahs to bats to whales to humans—that rule our planet today.

Leonardo da Vinci was a Renaissance genius. Not only did he paint masterpieces of art, but he was an obsessive scientist and inventor, dreaming up complex machines centuries ahead of his time, including parachutes, armored tanks, hang gliders, and robots. On the 500th anniversary of Leonardo's death, with the help of biographer Walter Isaacson, NOVA investigates the secrets of Leonardo's success. How did his scientific curiosity, from dissections of cadavers to studies of optics, shape his genius and help him create perhaps the most famous painting of all time, the "Mona Lisa"?

Journey to Florence to discover how Leonardo da Vinci used science, from human dissections to innovative painting techniques, to create his legendary artwork. Learn why Mona Lisa's smile is so captivating - and what it took to create it.