Katia Beauchamp, 29, and Hayley Barna, 28, came up with the idea for their now white-hot company Birchbox -- which delivers a box of beauty samples to subscribers every month -- during their final semester at Harvard Business School and launched the startup months later in September 2010.

"We thought, what if every woman had a key to the editor's closet?" said Ms. Barna.

Around Thanksgiving of 2009, they started brainstorming around the idea that discovering beauty products online felt impossible. After graduating, they started working out of another startup's space in Dumbo, Brooklyn, with just themselves, their editorial director Mollie Chen, and a friend who helped create the website.

Less than two years later, they're up to 65 employees and say they're well north of the 100,000-subscriber mark they last reported on in January. They've also partnered with a cross-section of brands ranging from the well-known, such as Kiehl's, Essie, Elizabeth Arden and Juicy Couture, to the emerging ones that are looking to gain entree into the U.S. market, such as French skin-care line Benta Berry.

Brands dole out samples for free looking to convert some paying customers. Meanwhile, Birchbox generates revenue off subscription fees ($10 a month for women and $20 for the recently launched men's line) and also sells full-size products on its site. It's also exploring sponsorships in the vein of a recent deal with the CW network's "Gossip Girl." May's box featured samples inspired by the show and hair and makeup tips from on-set stylists.

Birchbox grew thanks to the power of "discovery retail," or the notion of helping women discover beauty products they wouldn't otherwise find, according to the co-founders.

"From the brand side of things, we understood that the beauty industry had a need to better understand the ROI of sampling," said Ms. Barna.

"When we came up with the concept for Birchbox, [discovery retail] is the reason we thought it was powerful," said Ms. Beauchamp. "With beauty, you want to smell [something] and touch it."

Ms. Barna and Ms. Beauchamp think their idea could have legs outside the beauty realm and say that their subscribers are clamoring for them to offer samples in new categories. But for the coming year, they say they'll remain squarely focused on beauty.

Birchbox has raised two funding rounds for a total of $11.9 million.

What career advice would you have given yourself when you were starting out?

Ms. Beauchamp: You are going to work hard, that is ingrained in you. What you don't know is how crucial it is to drive your own career. Communicate your career goals and ask your managers what it will take to get there. Be deliberate and take responsibility. Don't leave things up to luck.

What is your favorite book?

Ms. Beauchamp: "The Great Gatsby." I love the escape to that world. Rereading it reminds me of when I began appreciating art for its ability to be both intellectually stimulating and a whimsical escape.

What's something most people don't know about you?

Ms. Beauchamp: I met my husband when we were 10!

If I wasn't doing this job, I'd be...

Ms. Barna: At another startup connecting with customers and building a product they loved. But in my total fantasy life, I'd be a florist!

What's something that people may not know about you?

Ms. Barna: I was published in an international science research journal before I graduated high school.

What career advice would you have given yourself when you were starting out?

Ms. Barna: You'll have a long and varied career. Don't overthink each step along the way. As long as you're learning and growing it won't be a mistake.

Have a dream vacation spot?

Ms. Barna: Right now a few sunny, lazy days in Italy sounds like the perfect vacation.