Some animals go through ‘metamorphosis’, changing from a baby into an adult that looks very different. While this change is happening, the young animal is vulnerable and needs to stay safe. Some young insects, such as moth caterpillars, build cocoons for extra protection. Moth cocoons are made of silk. Some caterpillars add other things to their cocoons, such as plant material, or even their own stinging hairs. This adds camouflage and another layer of safety. Some caterpillars build their cocoons underground, while others build them amongst the leaves they fed on. When the caterpillar has finished building, it becomes a pupa. It changes into an adult moth (metamorphosis) then hatches out of its cocoon.