In 1989, college senior Wendy Kopp was trying to figure out how to improve American public schools. For her senior thesis, she proposed creating a national teaching corps that would recruit recent college grads to teach in underserved schools. One year later, she launched the nonprofit, Teach for America. Today, TFA has 50,000 alumni, a budget of nearly $300 million, and continues to place thousands of teachers across the country. PLUS in our postscript "How You Built That," how a game of Secret Santa led Chris Waters to create Constructed Adventures, elaborate scavenger hunts for all occasions.