Bill Gates reflects on relationship with Steve Jobs and their last meeting

He made tens of billions as a computer industry pioneer and entrepreneur, but somehow Bill Gates has found ever more challenging problems to tackle. Tonight he talks with my co-anchor Bill Weir about his work to heal the world in tonight's Nightline Interview. As of tonight, Bill Gates is no longer the world's wealthiest man. But he didn't lose that title, he gave it away. And as a result, he can point to a different kind of scoreboard. How many lives do you think you've touched since you founded it? Well, it's easiest to measure in the health work, where over 5 million lives have been saved. Yes, the cutthroat businessman who once lived to release software is now more apt to release a jar full of mosquitoes to help raise malaria awareness. We'll let those roam around the auditorium a little bit. There's no reason only poor people should have the experience. And you may laugh when bloggers claim that he is better than Batman, but it's hard to find another single person who's done more to ease human suffering. You've almost eradicated polio from India. There was one case in a country of a billion people last year. Yeah, it was January 13, 2011. And so now we've had over a year of no polio cases in India. And we have 10 countries left that still have polio. We're very close. With a promise to give away 95% of their personal wealth, Bill and his wife Melinda's foundation has granted over $26 billion over the years. But their mission to save the world may get a lot more controversial with the release of his newest annual letter, which describes a plan to feed the world's exploding population with more genetically modified crops. They found this one rice that can survive flooding, and so they wanted to take the gene out and put it in with all the good genes, known as GMOs. These are seeds built in labs designed to grow stronger and more abundant crops. But by tinkering with nature, some worry they could accidentally spread disease, superweeds, and mutant insects. Several countries around the world refuse to grow them. Still, the Gates Foundation reportedly invested $27 million in biotech giant Monsanto, a leader in genetically modified crops. The question is, can these countries have their ability to choose if something's going to prevent starvation, and they see that the risks are extremely low, can they as a country have that choice? Big companies like Monsanto, they have the patents not only on the seeds, but the weed killer. And so farmers both in America and India then have to buy both in order to survive. It's very expensive. The seeds we're working on for the poor countries, there's absolutely no payments, no royalties of any kind. We go to the big companies and say, will you help us? And so they donate it. The Harvard dropout also has some interesting ideas on how to fix American schools, starting with peer review. He wants to let the top 2% of teachers float from class to class, teaching other teachers what works and what doesn't. So you think good teachers can be made? They're not born that way? Well, we can take the ones that are born that way, and there are plenty of those. And yes, we can't make you top 5%, but we can move you from average and help those teachers improve. There's been a little bit of distance now since the passing of Steve Jobs. I'm really intrigued by the anecdote at the end of Walter Isaacson's book about how in his final months, you came to his house and the two of you spent a couple hours together reminiscing and really made peace. He and I always enjoyed talking. He would throw some things out, some stimulating things. We'd talk about the other companies that had come along. We'd talk about our families and how lucky we'd both been in terms of the women we married. It was a great, relaxed conversation. How did his passing affect you? Well, it's very strange to have somebody who's so vibrant and made such a huge difference and then a kind of constant presence. It makes you feel like, wow, we're getting old. You look back and think about the great opportunities we had to have a big impact. Does it give you any added sense of urgency? Well, I hope I still have quite a bit of time for the focus I have now, which is the philanthropic work. You've got to stay healthy to see that happen. Malaria eradication, I need a couple of decades here to fulfill that opportunity. I don't think of myself as fading away, but it reminds you that you've got to pick important stuff because you only have a limited time.