Around the time Leonardo Da Vinci was painting the Mona Lisa, he was also writing his Codex on the Flight of Birds, a roughly 35,000-word exploration of the ways in which man might take to the air. His illustrations included diagrams positing pre-Newtonian theories of physics, a rudimentary plan for a flying machine and many, many sketches of birds in flight. The Mona Lisa, with her secretive smile, is a universe of intimacy captured on a relatively small panel of wood. But the landscape behind his captivating subject shows the world as you would see it from atop a tall hill--or from the vantage point you would get if you had hitched a ride on the back of a giant bird. Even as da Vinci was perfecting one way of seeing a face, he was dreaming of other ways of looking.

Of all the dimensions of Elon Musk that fascinate his fans--his intellect, his work ethic, his rockets, his dating life--there's one that hasn't been definitively explained: his seemingly self-restoring hairline. In early career moments, like a 1999 CNN segment that followed Musk getting a McLaren F1, or a 2000 image of he and Peter Thiel hyping PayPal, normal signs of male pattern baldness are visible. Since then, the CEO of SpaceX and Tesla appears to have found a solution, but it's his earlier incarnation that an experimental artist has plastered across San Francisco this week. And that artist has a theory. "I'm pretty blown away at how good his hair plugs are," says Katsu, whose mysterious posters appeared in San Francisco and New York City.