????Ben Silbermann can't stop staring at the refrigerators. The Pinterest co-founder and CEO and I are standing in the break room of his company's garage-size Palo Alto office. He's just flown back from Austin's SXSW interactive festival, and a redesign of his website is two days away. It's all a little overwhelming. But at this moment his full attention is focused on three glowing refrigerators. Sometime during his brief absence, a service has delivered them fully stocked and branded with the company logo. They're wedged into the tiny backroom behind the foosball table that three employees -- roughly 15% of his workforce -- are using for a conference. "I've been gone for one day, and it's so upscale," he says. "We used to just run to Costco all the time."
????That was before. Before Mitt Romney's wife, Ann, began organizing family photos on Pinterest. Before Reese Witherspoon gushed to Conan O'Brien that it was "a collection of the most amazing, wonderful craftiness on the earth!" Before the U.S. Army issued a guide for how to use it, and before Pinterest emerged as the fastest-growing website of all time. In March the site registered 17.8 million users, according to Comscore, a 52% jump in just one month -- and it isn't even open to everyone (would-be "pinners" must still request an invitation to join).
????Pinterest, for the uninitiated, is a deceptively simple-sounding, insanely addictive social media site that lets users collect and share images on digital pinboards. Most social-networking sites have first become popular among tech's early adopters along the country's coasts. But Pinterest found its most passionate users among the Midwestern scrapbooking set -- a mostly female group -- who have turned to it to plan weddings, save recipes, and post ideas for kitchen renovations.
????This growth has thrust Silbermann, 29, into the spotlight as investors and businesses alike try to figure out how they can get in on the action. Brands -- from large companies like Gap (GPS) and West Elm to online boutiques -- are tripping over themselves to establish a presence on it, and some are starting to reap the rewards of being "pinned," a de facto referral that prompts followers to click on product pictures to learn more. In February Pinterest drove more traffic to websites than Twitter, Google+, LinkedIn (LNKD), and YouTube combined. Meanwhile, the same (mostly male) investors who initially passed on Pinterest are kicking themselves. The company in October raised $27 million from venture capital firm Andreessen Horowitz in a deal that valued Pinterest at a reported $200 million. Marc Andreessen himself readily admits he didn't get it until a female researcher on staff urged him to reconsider. Says Andreessen: "Our industry historically … do we produce products initially aimed primarily at men or women? You'd have to say men."
????Amid all the noise, Silbermann must now build out a company that can keep up with Pinterest's user explosion. This type of hypergrowth has been a challenge for companies to manage -- remember the "fail whale" that signaled Twitter was suffering under the weight of its own popularity? In recent weeks Silbermann and his team have held a Monday meeting -- usually in the form of a coffee run to Bistro Maxine -- to figure out how to keep the site running on Thursday. (Writing a check to Amazon's web service unit usually does the trick.) Oh, and Silbermann must figure out how to make money. To that end, Fortune has learned, Pinterest just hired Tim Kendall, who spent many years as Facebook's director of monetization, to build out the business.
????Silbermann seems to be maintaining an almost eerily level head about Pinterest's success as well as the stress of running Silicon Valley's current "it" company. He talks so quietly that during our conversation I felt compelled to drop my own volume to match his. His eye is always on the wall-mounted flat screen that displays real-time data about how pinners are using the service. He takes a regular turn at answering customer-support e-mails, a mundane task that, he says, helps him make Pinterest even better. And while Pinterest's Palo Alto digs feature a poster with the words move fast and break things, a mantra at Facebook, Silbermann talks about Pinterest the way one talks about a fragile heirloom. "When you open Pinterest, it should feel like someone has hand-made a book for you," he explains. "Every item should feel like it's handpicked for you by a person you care about."
