Mammals are a class of vertebrate animals with hair, mammary glands to produce milk, and are endothermic. They have backbones and ingest food. Mammals are divided into monotremes which lay eggs, marsupials whose young develop further in pouches, and placentals where the embryo receives nourishment via a placenta connected to the uterus. Mammals have the most developed brains of animals, with potentiated memory and larger cerebrums in intelligent species enabling greater learning ability.