Melinda Gates is the co-chair of the Bill and Melinda Gates foundation. As head of one of the world's largest philanthropic organizations, she pushes to save lives and speak out on the developing world's toughest challenges. We spoke with Melinda late last month in Seattle, ahead of the release of the foundation's annual letter, and talked about how important it is to improve access to contraception, how to keep more women in science and technology, and the unique relationship she and her husband have with legendary investor Warren Buffett.