Check out this lettuce we regrew from a stump! We simply put it in water and set it in a place that gets partial Sun. Every few days we changed the water. That's it!
Lettuce is not the only food you can do this with, though. There are actually dozens of foods that can be regrown from the scraps and seeds people normally throw out.
We put together a list of 35 foods you can do this with, which you can check out here: https://offgridtiny.house/35-foods-you-can-grow-from-scraps/