Chitin is a tough, flexible polysaccharide that is found in the exoskeletons of many organisms. Here are some of the organisms that use chitin for structure and support:

* Arthropods: This includes insects, crustaceans, spiders, and centipedes. Their exoskeletons are made of chitin, providing them with protection and a rigid framework for movement.

* Fungi: Chitin is a major component of the cell walls of fungi, giving them their structural integrity.

* Some mollusks: While most mollusks use calcium carbonate for their shells, some, like squid and octopuses, have a chitinous beak that helps them to break open prey.

* Some algae: Certain types of algae also use chitin in their cell walls.

Interestingly, chitin is NOT found in plants. They use cellulose for their cell walls.