The Green Revolution focused on the big three - maize, rice and wheat - and the Green Revolution did not adapt the big three to African conditions, other than South Africa, as much as they should have.

Vaccines are extremely well tested; their safety is well understood. The false allegations about vaccines causing autism have been disproven. But there are still echoes out there confusing people.

You wish that you could move more rapidly and you have setbacks. You know, the AIDS epidemic was a huge setback for Africa, and it's only through generosity that we've avoided that just completely crippling an entire generation there.

The most interesting biofuel efforts avoid using land that's expensive and has high opportunity costs. They do this by getting onto other types of land, or taking advantage of byproducts that aren't used in the food chain today, or by intercropping.

It's the poorer people in tropical zones who will get really hit by climate change - as well as some ecosystems, which nobody wants to see disappear.

We have two other countries, Pakistan and Afghanistan - again it's the instability that is a problem there. So over the next several years, we expect to drive the number of [polio] cases back down to zero because that is likely to be the second disease after smallpox that we completely eradicate.

The finest pieces of software are those where one individual has a complete sense of exactly how the program works. To have that, you have to really love the program and concentrate on keeping it simple, to an incredible degree.