Granted, this may not be the way to solve the world’s hunger problems, but it’s a fun experiment.
Take the base from a stalk of celery, rinse it off, and put it in a shallow cup or jar of warm water on a window sill. Change the water daily and keep an eye on it to see if any regrowth begins. As you can see from the photos below, there were significant signs of regrowth within five days.