On Startups: "I hate it when people call themselves "entrepreneurs" when what they're really trying to do is launch a startup and then sell or go public, so they can cash in and move on.

The Mona Lisa, to me, is the greatest emotional painting ever done. The way the smile flickers makes it a work of both art and science, because Leonardo understood optics, and the muscles of the lips, and how light strikes the eye - all of it goes into making the Mona Lisa's smile so mysterious and elusive.

On the day he unveiled the Macintosh, a reporter from Popular Science asked Jobs what type of market research he had done. Jobs responded by scoffing, "Did Alexander Graham Bell do any market research before he invented the telephone?

Leonardo da Vinci was comfortable being illegitimate, gay, a misfit, a heretic. But he also respected other people. He didn't get into disputations. He was a genius but he had a certain humility. In his notebooks you see lists of people he wanted to grill about things like how the water diversions in Milan work; he was always interested in learning from other people.

Physics should represent a reality in time and space, free from spooky action at a distance.

Leonardo da Vinci had such a playful curiosity. If you read his notebooks, you'll see he's curious about what the tongue of a woodpecker looks like, but also why the sky is blue, or how an emotion forms on somebody's lips. He understood the beauty of everything. I've admired Leonardo my whole life, both as a kid who loved engineering - he was one of the coolest engineers in history - and then as a college student, when I travelled to see his notebooks and paintings.

Without Steve Jobs, you would have well-designed computers, probably open and not integrated, but they wouldn't have sex appeal, they wouldn't have romance.