The main characteristic of mammals is the presence of mammary glands, which produce milk to nourish their young. This unique feature allows mammal mothers to feed and care for their offspring, facilitating higher survival rates. In addition to mammary glands, mammals typically have hair or fur, three middle ear bones, and a specific structure in the brain known as the neocortex, which is associated with higher brain functions. Mammals are found in diverse habitats worldwide and exhibit a wide range of sizes, behaviors, and adaptations, making them one of the most successful groups of animals on the planet.