During the dot-com boom of the late 1990s, Jimmy Wales was running an internet search company. That's when he began to experiment with the idea of an online encyclopedia. In 2001, Wales launched Wikipedia, a website where thousands of community members could contribute, edit, and monitor content on just about anything. Today, the non-profit has stayed true to its open source roots and is one of the ten most visited websites in the world. PLUS in our post-script "How You Built That," we check back with Leigh D'Angelo, who explains how her sister's break up inspired them to create a dating app—for dog owners.