Amazon is buying Whole Foods - here's Amazon's vision for the grocery store of the future

Amazon is buying Whole Foods in a blockbuster $4. 

It's not clear yet what Amazon plans to do with the upscale grocery store, but one thing is clear: Amazon 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, $4, doesn't work like a typical Walmart or supermarket - instead, it's designed so that shoppers will use an app, also called Amazon Go, to automatically 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 can automatically identify 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 Amazon account.

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

Last year, Amazon internal plans show it could build 2,000 grocery stores across the US in the next decade, $4. $4 opened to the public in Seattle earlier this year. 

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