The "0-3 months" stage refers to the early developmental period of infants, where they undergo significant growth and change. During this time, babies typically gain weight rapidly, often doubling their birth weight by around five months. They also begin to develop basic reflexes, such as grasping and rooting, which help them interact with their environment. In these first few months, infants primarily communicate through crying, which signals their needs, such as hunger or discomfort. They start to focus on faces and can recognize their primary caregivers, fostering early social connections. This period lays the foundation for future emotional and cognitive development.