Platform businesses reshape industries by using software to create new markets. But it’s hard to see how by looking from the outside in. We interviewed 33 platform businesses, including DoorDash, Dropbox, Philips, and Stripe, to find out how they did it. The answer? Start with a real customer problem, one you can solve with a service delivered via an API. As a digital business leader in an incumbent firm, your biggest opportunity is to develop a platform to deliver new services to existing customers or take your differentiated value into adjacent markets.