Block Got Its Start Selling Payment-Processing Hardware, but That's Now Less Than 1% of the Business. You'll Never Believe What Its Top Revenue Stream Is Now.

When financial technology (fintech) company Block (SQ 0.31%)went public in 2015, back when it was known as Square, it explained its business in its registration documents like this: "We started Square in February 2009 to enable anyone with a mobile device to accept card payments, anywhere, anytime." The company had a square-shaped credit card reader that plugged right into smartphones and tablets.Block has more hardware devices today, and many people think of these devices when thinking about the company. H ...