Today, at 43, Melinda Gates is ready to reveal her full self – to go public, so to speak. “I had always thought that when my youngest child started full-day school I’d step up,” she says, sitting down with Fortune for her first-ever profile. Although she admits she would prefer to stay out of public view forever, her older daughter got her thinking. “I really want her to have a voice, whatever she chooses to do,” she says. “I need to role-model that for her.” She is spending more time on foundation work, up to 30 hours a week. “As I thought about strong women of history, I realized that they stepped out in some way.”

….Buffett also believes that Melinda makes Bill a better decision-maker. “He’s smart as hell, obviously,” Buffett says. “But in terms of seeing the whole picture, she’s smarter.” Would Buffett have given the Gates Foundation his fortune if Melinda were not in the picture? “That’s a great question,” he replies. “And the answer is, I’m not sure.”

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