There's 20 companies that I have investments in - some batteries, some solar-thermal, one big nuclear thing. We need hundreds and hundreds of companies like that, so that in a 20-year time frame we really are starting to change the energy infrastructure.

Learning from mistakes and constantly improving products is a key in all successful companies.

The market does not drive the scientists, the communicators, the thinkers, the government to do the right things.

Success on the Web require high-level corporate understanding of the Internet's capabilities and support of early test-and-invest projects.

But the improvements will happen faster and last longer if we can channel market forces, including innovation that's tailored to the needs of the poorest, to complement what governments and nonprofits do. We need a system that draws in innovators and businesses in a far better way than we do today.

Microsoft's only factory asset is the human imagination.

It is a high bar to say that it's more fun than working on software because the work at Microsoft that both Melinda [Gates] and I did was thrilling. We were making breakthroughs and empowering people.