Sweetgreen builds a brand beyond a bowl of greens

A salad chain dreamed up by three college seniors is shaking up the restaurant business, and building a brand that goes beyond fresh salads. Sweetgreen is now open in 30 locations, from Washington, D.C. to Boston and California, and just last week, the company announced a much bigger bowl of green: nearly $100 million in total venture funding.

Their assembly-line salads draw a cult-like following, reports CBS News correspondent Julianna Goldman. For hours each day, people line up out the door, hungry for a creative menu that changes each season.

Three friends-turned-Sweetgreen founders Nicolas Jammet, Jonathan Neman and Nathaniel Ru are redefining healthy fast food and trying to disrupt the $5 trillion food industry in the same way chains like Chipotle have eaten into fast food staples like McDonald's and Burger King.

"For us, eating healthy meant understanding your food and knowing where it came from," Jammet said.

At Sweetgreen, there are low-calorie options, but that's not the norm. Fresh ingredients -- and where they come from -- are the focus. It's farm-to-table in a mass supply chain.

"That's exactly the disruption in the industry that we want to create; that you can have a national restaurant brand that still sources locally and does things right," Neman said.

They hatched the idea as students at Georgetown University and opened their first store in 2007, just steps from the apartment they shared in their senior year.

"We were on our way over to grab some lunch and John turned to me, 'What about this spot?'" Ru said.

The transition from friendship to operating a multi-million dollar business didn't happen overnight, but they were fueled by their shared passion for food.

"We realized this was more than something Georgetown needed. It's something D.C. needed, and the rest of the country needed," Jammet said. "This was the way people wanted to eat."

In 2014 they brought in $50 million in revenue -- up more than 50 percent from the year before, and a figure they expect to surpass this year.

"I had a sense that something special was brewing there," billionaire investor and AOL co-founder Steve Case said.

Case has raised millions for the company. He sees the salad chain as changing the face of "fast-casual" by tapping into health trends and technology. Customers can use an app to order and pay before picking up their food.

But Case said there's something more: "It's about the experience you have when you are there with other people, a sense of community," Case said, "and that's really what has made it more than just an average, kind of fast-casual restaurant."

The founders said they always knew they wanted more than a restaurant. That's one reason they host a music and food festival each year that attracts thousands. They want to build a community committed to better living, a concept they call the Sweetlife.

"It's this lifestyle brand that we believe people want to associate with. And it's not about eating healthy to diet," Ru said. "It's about eating healthy as part of a lifestyle choice for better living."

So are they living the Sweetlife?

"100 percent," Ru said.

They still eat at Sweetgreen seven days a week, and every new employee has to work the salad line. In fact, when CBS News visited one of their stores, the new CFO was learning the ropes and cutting cucumbers.