An exoskeleton is a rigid, external covering for an organism's body. It typically consists of a hard, protective outer layer made from materials such as chitin or calcium carbonate, which provides support and protection to the animal. Examples of animals with exoskeletons include insects like beetles and cockroaches, crustaceans like crabs and lobsters, and some species of mollusks like snails and clams. The exoskeleton grows along with the organism as it develops, and is periodically shed or molted to allow for growth.