Smaller kinds of lobsters are sometimes called "lobsterettes". Lobsters do not have bones. They have hard shells which protect them. This hard shell is made from a material called chitin. The shell is so hard that lobsters must climb out of them before they can grow bigger. This is called "moulting". When lobsters moult they are weak and easy to attack. If they hide for long enough they will grow a new hard shell and the lobster will be bigger. Some lobsters change color when they grow a new shell. Lobsters can grow new parts of their body when they lose them. Every time they moult the body part will get a little bit bigger and stronger until it is back to normal.