Editor's note: Sweetgreen is one of Inc.'s 2015 30 Under 30. This year's readers' choice winner is ThinkLite.  

When the three co-founders of fast-casual dining chain Sweetgreen were students at Georgetown University, they were frustrated because they couldn't find a place to eat that was healthy, approachable, and that "aligned with our values," says Nathaniel Ru. So, Ru, Jonathan Neman, and Nicolas Jammet decided to start a restaurant of their own. They raised $375,000 from friends and family and launched their first Sweetgreen location in August 2007, a few months after graduation, in a 580-square-foot space near the university campus--and across the street from Neman's apartment. It was profitable in the first year and they opened two more D.C.-area stores within 18 months.

"Values-aligned" dining seems like an unusual focus not just for a business but also for a bunch of college seniors, who are traditionally more preoccupied with finding the cheapest place to buy beer. But it was because of their focus that the trio succeeded, says William B. Finnerty, an adjunct professor at Georgetown and a managing director with UBS Private Wealth Management. Each Sweetgreen founder took Finnerty's entrepreneurship class while at Georgetown, and each took away the same key lesson: It's possible to build a successful business that meshes with your personal values.

Since they launched those first three stores, assisted by Finnerty's lessons, mentors (including Finnerty and restaurateur Joe Bastianich, for whom Jammet had once interned), and $57.5 million in funding (including an early investment by Finnerty), the Sweetgreen guys have created a chain of 29 restaurants in the Eastern U.S. that focus on organic, healthy foods. They have over 100 full-time and 900 part-time employees and have expanded what they call their "culinary lifestyle brand." Now, there's the annual Sweetlife Music and Food Festival, which Sweetgreen founded and which attracts over 25,000 people, Sweetgreen in Schools program, which has reached over 4,000 kids so far, with lessons about healthy eating, and Sweetgreen Passport, which offers localized fitness and lifestyle events.

Neman attributes Sweetgreen's success to several factors. First, he says the team works to create the best possible employee environment by building a strong leadership team in each location (store general managers are called head coaches). The head coaches are responsible for the overall culture in each store. This includes paying more than minimum wage, creating a training and leadership development program, promoting from within, giving employees quality uniforms they can feel proud to wear, and scheduling team building experiences, such as picnics, "secret gifting" events, and a "Shades of Green" program that rewards employees with gifts as they hit various milestones (including a pair of green Chuck Taylor Converse sneakers on their first anniversary).

The second factor is keeping things simple--which they learned the hard way in their first, tiny store. "They've taken a very reductionist approach to a very complicated and jammed industry," says Finnerty. "That first small place, which seemed to be an obstacle, has been a key to their success."

Lastly, they've evolved their menu from just salads to a wide range of dining options. "If we'd kept the same menu, we wouldn't have survived," says Neman. To help them with their latest evolution, they recently hired their first culinary director, Michael Stebner, who is designing seasonal, localized menus for all their locations, to be updated five times yearly. "Since he has joined us, it's been exciting to see how much better our food has become," says Jammet.

The long-term vision is to expand into even more markets, including the West Coast this year, and to build on their branded events. "Our mission is to be the number-one healthy-lifestyle brand in the world," says Ru. "As we grow and evolve, we'll be focusing on our 'why,' which is the idea of the sweet life--living inspired by passion and purpose."