The stock trading app only launched cryptocurrency trading a few months ago. : Robinhood, the free stock trading app, has raised $363 million in a new investment round valuing the company at $5.6 billion. The Series D round, announced Thursday, makes Robinhood the second most valuable private fintech startup in the U.S. after Stripe, the online payments company. Bucking the model of traditional brokerages—which rely on trade commissions to make money—the three-year-old Robinhood has shown an ability to rapidly overtake incumbents in one of the oldest Wall Street industries.