It is present all around us, in plant and animal creatures. It is sometimes considered to be a spinoff of cellulose, because the two are very molecularly similar. Cellulose contains a hydroxy group, and chitin contains acetamide. Usually, polymers are man-made. Crabs, beetles, worms and mushrooms contain large amount of chitin.
Chitin is a very adaptive material for a creature.
Insects and animals with chitin coats usually shed these coats, or molt, at least once a year. Chitin is a very firm material, and it help protect an insect against harm and pressure. Depending on its thickness, chitin can be rigid or yielding. Often, insect coats contain thick, stiff layers of chitin. The areas around legs and face contain very thin, pliable layers.