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Ben Rattray

Change.org

In his senior year of college, as Rattray prepared for a career in banking, he had a defining moment that radically altered his sense of self and his future ambition. On a trip home over winter break, one of his younger brothers, Nick, came out as gay. The development was difficult for Ben's family and for Nick, who had been struggling socially in school. It prompted some soul-searching for Ben when Nick criticized him for being the sort of person who had made the coming-out process most difficult and painful. Nick said he was less hurt by people who were actively homophobic than those who stood by and said nothing -- like his brother.

At that moment, Rattray dedicated himself to "never staying silent again." He developed what he calls "the grandfather test," in which he considers his decisions and actions as he -- and his loved ones -- might perceive them decades down the road. Would he be proud of what he'd done? Would he have regrets?

He also became fixated on a question: How do you make the ideal democratic society? How do you empower people to come together and advance issues they care about? How do you "democratize democracy"?

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Katrina Markoff

Vosges Haut-Chocolat

In 1998, Markoff moved to Chicago, where she set up a kitchen in her Logan Square apartment. That first year she worked zealously making chocolates and in 1999 successfully courted Neiman Marcus. Carrying a box of her Naga truffles, she walked into the epicurean department of Neiman's big Chicago branch and asked for the manager. She showed him her chocolates and said she'd like to sell them there; he thanked her, took them, and threw them on a table in the break room. The next day he called and said he had to order more immediately; the staff had eaten all of them in minutes and was demanding more. He ordered some for the store to sell too.

From there she landed Whole Foods (WFM). It all happened so quickly that she was still making the chocolates by hand. "I was selling to Neiman Marcus out of my house," she says. "I touched every single truffle."

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Marissa Mayer

Yahoo (YHOO)

Mayer had a willingness -- or even a willfulness -- to do things before she was ready. During a summer break from Stanford, she worked in Switzerland and had "an aha! moment" while shopping for food. "The first day, I went to the grocery store and got in trouble because, it turns out, you buy produce in Europe completely differently [from in America]," Mayer explained at a Fortune Most Powerful Women event in 2010. She simply wanted to buy grapes (a fruit she so loved as a kid that her family nicknamed her "the Grape Ape"), but she couldn't master the process of weighing the fruit and printing the price sticker.

"This woman just started yelling at me in German," Mayer said. "I remember going back to my apartment and being like, 'What was I thinking? I don't speak the language. I can't even buy produce here.' " The moment was hardly traumatic, but it made her realize that doing something you're not ready to do is how you grow. "It's when you move through that moment of discomfort of 'Wow, what have I gotten myself into this time?' "

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Scott Harrison

charity: water

At 2 p.m. one day in August 2004, in Uruguay's trendy resort town of Punta del Este, Harrison was just waking up. He stumbled out onto the beach, squinting into the sunlight, with a raging hangover. He was in the middle of a weeklong bender on a spring-break-style vacation. The trip's fireworks tab alone totaled $1,000.

Harrison had spent the better part of a decade professionally schmoozing as a nightlife promoter in New York City, dabbling in drugs and dating models. But that day under the harsh South American sun, he says, he came to a sudden and stark realization: "I was the worst person I knew."

That jolt of self-awareness spurred the 28-year-old to turn his life around. He quit using drugs. He quit smoking. He quit dating models. And he founded charity: water, a wildly successful nonprofit that has raised millions to deliver clean water to people in the developing world: It has completed more than 8,000 water projects in Africa, South America, and Asia.

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