Brothers Patrick and John Collison founded and sold their first company before they turned 20. They created software to help eBay users manage inventory online, which set them on a path to help make e-commerce frictionless. Today, John and Patrick are the founders of Stripe, a software company that used just a few lines of code to power the payment system of companies like Lyft, Warby Parker, and Target. PLUS in our post-script "How You Built That," we check back with Kirby Erdely, who saw a problem with flying beach umbrellas and developed a new kind of tent stake—with a twist.