Babies are young humans typically defined as being from birth to around two years old. They undergo rapid physical and cognitive development during this time. Newborns are usually dependent on their caregivers for nourishment, comfort, and safety. They communicate primarily through crying and gradually begin to develop social skills and motor abilities. During the first year, babies grow quickly, often doubling their birth weight by six months. They start to explore their environment, reaching for objects and learning to crawl. By the end of their second year, many babies can say simple words and may begin to walk, marking significant milestones in their development.