Warby Parker, a fashionable eyeglass company based in New York City, has seen some explosive growth in the last year. The company launched in 2010. Since then, the start-up has scaled to 60 employees, grown 500 percent, and has already moved into bigger offices--twice.

The company's business model is simple: Glasses, including lenses, are $95. There's also a component of social good: for every pair bought, a pair is donated to someone in need. About 50 percent of the company's sales are driven by word of mouth--a testament to the strength of the company's story. In short, people are proud of Warby Parker, and want to share the company's mission with their friends and family.

The company's co-founder, Neil Blumenthal, addressed a crowd of more than 550 entrepreneurs and business owners GrowCo this week. He offered a bit of insight into how and why the company has grown so rapidly, and how your start-up can steal a bit of wisdom from Warby. 

1. Cut out the middle men.

Why are glasses traditionally as expensive as, say, an iPad? The answer to that question can be summed up in one word, explained Blumenthal: Luxotica. Luxotica is a $7 billion multi-national corporation that pretty much owns the eyewear industry--from Ray Ban to LensCrafters. By working with a manufacturer in China, and designing the glasses themselves, Blumenthal and his co-founders were able to cut out the middle men and make the glasses far more affordable.

"We were able to transfer billions of dollars from these multinational corporation to normal people like you and me," Blumenthal says.

2. Don't overspend on unnecessary marketing.

Guess how much Warby Parker spent on marketing and advertising when they launched? $10,000? $100,000? The correct answer is zero. The company launched with two well-placed editorials in Vogue and GQ. When the magazines hit newsstands, the Warby Parker site crashed. Within two weeks, they had sold out of 15 styles of eyeglasses, and had a waitlist of 20,000 customers. In fact, the company only recently (about six months ago) began marketing on Google AdWords.

3. It all comes down to company mission.

When the company moved into their new offices a couple of months ago, Blumenthal and his co-founder, David Gilboa, decided to knock down the walls of the office. Why? "It gives visibility to everyone there," he says. "We want to institute mechanisms for people to learn on a regular basis."