How Does Amazon's Checkout-Free Grocery Store Work?

Amazon revealed its first brick-and-mortar grocery store on Monday in Seattle. The Amazon Go store features no lines or checkout counters, using sophisticated technology in its place, calling the new model "Just Walk Out" shopping. 

Here's how it works: when you arrive at the store you check-in on your phone and take whatever you want off the shelves. When you leave, it's all charged automatically to your Amazon account.