Seaweed is a general name for the many kinds of algae that grow in oceans, seas, and other saltwater environments. Unlike true plants, which have roots that draw nutrients from soil, seaweed absorbs everything it needs directly from the water around it. Some seaweeds are tiny and delicate, while others, like giant kelp, can grow over 100 feet long, creating underwater forests where fish and sea creatures live.

Seaweed comes in different colors: green, red, and brown. The brown seaweeds include kelp, which you might see washed up on the beach in long, rubbery tangles. People around the world eat many types of seaweed. The crispy dark green sheets wrapped around sushi are made from seaweed called nori. In Ireland, people harvest a red seaweed called dulse and eat it as a snack. Asian cuisines use seaweed in soups, salads, and many other dishes.

Seaweed also has uses beyond food. Scientists extract compounds from seaweed to make ice cream smoother, toothpaste thicker, and even to create biodegradable plastics. Some seaweeds are also used as fertilizer for gardens because they’re rich in nutrients that help plants grow.