Biological processes are exhibited through the physical changes an individual undergoes through the course of their life that include both normal and abnormal development in the body characterized by patterns of physical growth and maturation. Physical developments manifest in the form of healthy and unhealthy behaviors referring not only to anatomical growth in height and weight, but the development of gross and fine motor skills. If a child's nutrition is inadequate, or if she is exposed to harmful substances such as alcohol (in pregnancy), her growth and development may be hindered. For this reason, many programs exist to educate people on the importance of childhood nutrition and health, including during pre- and post-natal periods.
In infancy and toddlerhood, from birth to two years of age, major physical developments are the continued growth of the brain and its increasing complexity, in addition to the body's rapid physical growth and motor skills development. It is categorize as the period from about four weeks to about one year old and toddlerhood from about one year, when an infant begins walking, until about age two or three. During their first two years, human develop faster and grow more rapidly than any other two-year period of life. Around four months of age, a baby discovers his own fingers and may spend much of his waking time studying them. From five to eight months, a baby begins learning fine motor skills, hand-eye coordination and usually learns to crawl. From nine to twelve months, babies enjoy learning social games, learn to feed themselves, and may take the leap from crawling to walking. By twenty-four months, he is officially a toddler exploring the world around him. He is able to express his feelings more clearly and understand simple right from wrong.
In children, early childhood, ages two to six years, includes physical developments of steady growth and an assumption of more adult-like body proportions, while appetite tends to diminish and sleep problems commonly occur.