Melinda Gates is analytical and driven, not unlike her husband. She likes hard facts, strict accounting and expects everyone around her to measure up - very much the CEO.
She talks about spending a billion here, a billion there, and you realize that billionaire philanthropists aren't like you and me. There was a funny moment when she was going through some figures and in an uncharacteristic slip she said she'd pledged one billion to vaccines when it's actually ten billion.
"You know, it just occurred to me you had misplaced nine billion dollars. Now, I misplace change at the end of the day. But you had actually forgotten about nine billion dollars," Pelley pointed out.
"I think I missed a zero in there," she replied.
"Most people would remember that kind of a number," Pelley said.
"You know, for me, I think more about the possibility of what it is we're trying to change. So, if I have to go around the health statistics in the world, I don't tend to get those wrong. But the amount of dollars we put in, I'm always more focused on what's the result we're gonna get, no matter how much money we've put into the issue," Gates said.
"Now I'm from Texas too, so I can say this. You don't wear your wealth like a Dallas gal. You don't seem to be a big consumer of jewelry and cosmetics," Pelley remarked, referring to Gates' toned-down style.
"I don't find great joy in those things. I find much more joy in connecting with people. I'm much more at home being what I call 'out on the ground,' doing this work. And for me, that's where I find meaning. I don't find meaning in material things," she replied.
One village they visited had nothing material to give but music.
"You know, it's a long way from Microsoft," Pelley said.
"And I like this a whole lot better," Gates said.
Some 7,000 miles away, back home in Seattle, the Bill and Melinda Gates Foundation is building its new headquarters. There are 850 employees figuring out which science or development projects are worthy.
And listen to what they have spent already: $4.5 billion for vaccines; almost $2 billion for scholarships in America; and $1.5 billion to improve farming in Africa and Asia, just to name a few. The foundation's wealth ranks up there with America's biggest companies, just behind McDonalds and ahead of Boeing.
"Boy, his and hers offices. I'm not sure a lot of marriages would survive this," Pelley said, touring the Gates' workspace.
"Oh, it works out great," Bill Gates said.
"Well, we actually like it a lot," Melinda Gates added.
The Gates live in a secluded hi-tech mansion with three children. The kids are now ages 8, 11 and 14. Bill and Melinda met at a Microsoft meeting 23 years ago.
"What did you think? I mean, it is not everyday a girl gets asked out by the richest man in the world?" Pelley asked.
"Oh, no, It wasn't that, it was that I didn't think it was a very good idea to date the CEO of the company," she replied.