Chitin is a polymer that can be found in anything from the shells of beetles to webs of spiders.
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.