A nest is a structure prepared by many animals for the protection of their eggs and young, or for sleeping purposes. In social insects, the nest provides the home of the whole colony, and may have special structures for temperature control and ventilation. The sleeping nests of, for example, the great apes, are commonly no more than crudely woven hammocks of twigs and branches. The sleeping nests of other mammals (which may be used for hibernation) are as complex and woven as any breeding nests. Both these and the nests used by birds and mammals for breeding, must protect the animals within from both weather and predators. Nests can be built of mud, leaves, twigs, down, paper, and various kinds of human garbage.