Like a lot of great innovators, Ida Tin wanted something that didn’t exist, so, she built it. It’s a period tracking app called Clue, and the more you tell it—about your mood and your cycle—the more it can tell you about your reproductive health. On the surface, Clue is a tool for individuals to track menstruation. But Ida's real goal is nothing short of transforming women's health around the world. She’s part of a new wave of renegade thinkers who believe that everyday data can give everyday people more power over their lives.