Yessotoxin is a big word that refers to a type of toxin that comes from tiny organisms called algae. Algae are like tiny plants that grow in the water, like a pond or the ocean.
Sometimes, when there are lots and lots of algae in the water, they can make yessotoxin. If people or animals drink or eat something that has yessotoxin in it, they might get sick. Yessotoxin can make people feel nauseous, which means they might feel like they want to throw up, and it can also make their stomach hurt.
Scientists are studying yessotoxin to learn more about how it works and how to keep people and animals safe from it.