If empathy channels our optimism, we will see the empathy and the diseases and the poor school. We will answer with our innovations and we will surprise the pessimists.

Going out in the field, it's always enlightening to see what's working and what's not and to sit down and talk - I was with young girls in south Africa - understanding why our tools for prevention aren't being adopted, and what way may need to invent to help protect them.

Whenever you have a few setbacks, the idea that half as many children are dying now as back in 1990 and so... it was over 12 million a year, now it's less than 6 million a year. We have a clear path to get that under 3 million a year and we know what to do. And this generation of young Africans is a very large group.

Whenever you have multiple devices including multiple PCs that you want to share information with, it's always been a bit complicated.

I've been studying how quickly we can get energy out to the poor countries - a lot of which are in Africa - and how little progress we've made there. There's no more electricity today in sub-Saharan Africa per person than there was 20 years ago.

In the old generation, if one kid bought a PlayStation 2 and the other kid bought an Xbox, at his house you played PlayStation, at your house you played Xbox. Now that it's online, all those early buyers who... you want to play with, they've got their reputation online of who they are and how good they are at these games.

Life's not fair, get over it!