Amazon said on Friday it was buying Whole Foods in a blockbuster deal for $13.7 billion.

It's not clear yet what Amazon plans to do with the upscale grocer, but it has big plans for the future of grocery stores.

The online retail giant revealed a concept for a physical store in a video in December.

The store, called Amazon Go, doesn't work like a typical Walmart or supermarket — instead, it's designed for shoppers to use an app, also called Amazon Go, to add the products they plan to buy to a digital shopping cart. They can then walk out of the building without waiting in a checkout line.

The idea is that Amazon's machine-learning technology automatically identifies when a product is added to your cart, so you don't have to do it yourself. When you leave the store, Amazon automatically charges your account.

The stores would sell ready-made food, staples like bread and milk, and other grocery products. Amazon says its stores would be about 1,800 square feet — relatively small compared with big supermarkets.

Last year, Amazon's internal plans showed that it could build 2,000 grocery stores across the US in the next decade, Business Insider reported. The first Amazon Go store opened for Amazon employees in Seattle earlier this year.

Here is what Amazon says it would be like to shop in one: