Hopefully, whether it's energy or child vaccines, the case of the many benefits helping countries so that they are stable, so these refugee problems that have been troubling for Europe - a little less so for the U.S. but, even so, a lot of controversy there - these things are why the future's going to be better than the past. People really do look to the United States, so we'll be there making the case.

[Melinda Gates] is a lot of fun to work with. There's some of the people skills that she's better at and cares about more. It'd be a mistake not to think of her as very numerical and interested in the science. I enjoy, if I get ahead of her, say, understanding the immune system, then we can spend a few hours, where I'm going through how amazing it is and interesting, and how that affects our creating new products, so I've always had a partner.

Eventually we'll be able to sequence the human genome and replicate how nature did intelligence in a carbon-based system.

[Africa] is the one continent where you still have a lot more young people than old people. So making sure they're healthy, good nutrition, good education. That'll be important for the world.

At some point, that risk-taking private capital can take over, and have patents and trade secrets and things that let them lead the way, which happened with the steam engine and some other things, although with energy, the time of adoption is a lot longer than it is with, say, IT products or even medical advances, like drugs and vaccines.

I was lucky to be in the right place at the right time. But many others were also in the same place. The difference was that I took action.

The death of a child is an incredible tragedy all over the world. Back in 1990, about 12 percent of children were dying before they reached the age of 5.