Bill Gates: It's an inspiration that one person off on their own, with no positive feedback, nobody ever told him, you know, it was right or wrong. That he kept pushing himself. You know, found knowledge in itself to be a beautiful thing.
Gates scoffs at any comparison to the great Leonardo, but a look around his private office reveals a man equally obsessed with understanding his world.
Charlie Rose: Can I look at these?
Bill Gates: Sure. This is the weather one, "Meteorology." My very first course that I watched was this geology course.
Charlie Rose: This is a whole series on the joy of science? "Mathematics." "Philosophy in the Real World."
Gates' collection of DVDs contains hundreds of hours of college lectures that this famous Harvard drop-out has watched.
Bill Gates: The more you learn, the more you have a framework that the knowledge fits into.
When he's on the road, Gates - who's a speed-reader -- lugs around what he calls his "reading bag." When he finishes a book, he posts his thoughts on his website, "Gates Notes."
Bill Gates: What I'll do is, I'm reading these books.
Charlie Rose: Oh, look at that.
Bill Gates: I'll take notes.
Charlie Rose: Oh these are your notes already?
Bill Gates: Right.
Charlie Rose: Look at this.
Bill Gates: I love to take notes on books. So I just haven't written it up yet.
Charlie Rose: How long will it take to read all of this?
Bill Gates: Oh, a long time. Thank goodness for vacations. I read a lot.
But Gates isn't just reading books for pleasure, he is determined to use his knowledge to back groundbreaking innovations. Take this high-tech zapper. It is a laser designed to shoot down malaria-infected mosquitoes in mid-flight.
And Gates showed us one of his boldest, and he says most important, ventures -- a new kind of nuclear reactor. It would burn depleted uranium, making it cleaner, safer and cheaper than today's reactors.
Bill Gates: And your fuel will last for 60 years. So during that entire time, you don't need to open it up, refuel it. You don't need to buy more fuel. So there's a certain simplicity that comes with this design.
Charlie Rose: And when could it come on stream?
Bill Gates: Best case would be to have a prototype around 2022.
Bill Gates calls himself an "impatient optimist" - a description his wife Melinda says was accurate even when they met over 20 years ago.
Charlie Rose: Melinda, what did you like about him?
Melinda Gates: Just his curiosity and his optimism about life and this belief that, you know, that you can change things. I mean he believed that clearly in Microsoft. He was changing the world with software and he knew it.