By Susan Choung for Food Network Kitchen

It sounds like something out of a futuristic robot movie: Cut off the green part of a scallion and it regenerates itself like a Terminator. Regrowing vegetables in water isn't sci-fi, though. It's a real-life no-waste hack you can do without any soil. Not only does it save money, it's a fun little project you can tend to like a low-maintenance, edible chia pet.

The process is almost suspiciously simple: Pop the white parts of the scallions in a glass with a bit of water, park it by a window and the greens will sprout. You might be asking, "Okay, but what's the catch?" None, really. You have to change the water every day or so and that's about it. Here's how to do regrow your own:

1. Stand the white parts of the scallions, with the wispy root ends down, in a glass or jar.
2. Add water to cover the roots.
3. Place them by a window that gets plenty of sunlight.
4. Keep the water fresh by changing it every one to two days.
5. Watch the greens shoot up within a few days.
6. Snip off the greens, as needed.

Scallions are the easiest vegetable to regenerate this way but this method also works on the following:

Lettuce

You'll get a few leaves at a time — just enough for your sandwich.

1. Place the stem end with a few inches of the lettuce intact in a shallow dish of water.
2. Place it by a window that gets plenty of sunlight.
3. Keep the water fresh by changing it every one to two days.

Celery

A few stalks will regrow, which is plenty, because who ever uses the whole bunch of celery at once?

Similar to the steps for lettuce, place teh stem end in a shallow dish of water, by a sunny window. Change the water frequently.

For better results, poke toothpicks into the sides of the celery to prop up it up. You want to submerge the celery but keep the bottom from touching the dish.

Fennel

It has a pronounced anise flavor that's divisive. This way, you can grow back the green shoots for just the members on team fennel.

Follow the same steps for lettuce and celery, using the bulb end.

Bok Choy

Green leaves will sprout from the stem end. You can add them to a soup or stir-fry.

Follow the steps for regrowing lettuce.

Recipes to try:

Miso-Glazed Salmon Cold Noodle Salad

Ultimate BLT

Simple Bolognese

Salmon and Vegetable "Stir-Fry Cheat Sheet"

Related Links:

Produce Scraps You Should and Shouldn't Eat

Homemade Chinese Takeout Favorites

How to Prep Your Produce