Newborns are infants who are typically defined as being from birth to about two months old. During this stage, they undergo rapid physical and developmental changes. Newborns usually weigh between 5.5 to 10 pounds and measure about 18 to 22 inches in length. Their senses are developing, and they can recognize their mother's voice and smell. At this age, newborns spend most of their time sleeping, often up to 16 to 18 hours a day. They communicate primarily through crying, which signals their needs, such as hunger or discomfort. Proper care, including feeding and regular check-ups, is essential for their growth and health.