When Katia Beauchamp and Hayley Barna launched Birchbox from business school in 2010, they set out to disrupt the beauty industry by delivering monthly samples in a box. Even though people told them the idea would never work, Birchbox attracted hundreds of thousands of subscribers and enthusiastic buzz as a subscription pioneer. But the speedy success was overwhelming for Katia; over the years the company endured plenty of growing pains as it found its distinctive voice in the beauty industry. PLUS in our postscript "How You Built That," after noticing that many of her female friends hated buying cars, Athena Staton launched SheCar, a personalized online service for used car buyers.