Nat Turner was 24 when he sold his first company for $80 million. He sold his next one this past February – this time, it was for $2 billion. Nat Turner is the cofounder and CEO of Flatiron Health, a company that's changing the way cancer researchers collect data, with the goal of transforming the way patients are treated. He was inspired to start the business when his younger cousin was diagnosed with leukemia. And while he's been an entrepreneur since he was a kid — in high school he had a thriving snake breeding business — he feels emotionally connected to Flatiron in a way he never had with his past companies. On this episode of "Success! How I Did It," Business Insider's Rich Feloni speaks to Turner about why he built Flatiron Health, what breeding reptiles taught him about entrepreneurship, and the importance of believing in your company's mission.