A common characteristic of mammals is the presence of mammary glands, which produce milk to nourish their young. This unique feature allows mammalian mothers to provide essential nutrients and antibodies to their offspring during early development. In addition to mammary glands, mammals are characterized by having hair or fur (at least at some stage of life), three middle ear bones, and a specialized jaw structure. They are warm-blooded animals, allowing them to maintain a constant body temperature, which helps them adapt to varying environments.