During the first three years, children are constantly growing and acquiring new skills and knowledge. Surveillance systems have shown that injury is the leading threat to the health and well-being of young children.

Infants depend on their caregivers for food, warmth, and care, and for meeting such basic needs as eating, diapering, sleeping, and bonding. But all babies are unique. Some infants may settle easily and be capable of quickly soothing themselves.

The toddler years are a time when children are building skills in all areas. They remember what they learn and share it with others. They understand things more deeply, make choices, and engage with others in new ways. The changes in their physical, cognitive, and social-emotional development help them to build new skills that prepare them for school and later learning.

By the time they are preschool-aged, children are more independent in their play and their ability to meet their own needs. They focus on learning rules and routines to know what is safe and appropriate. Their constant dialogue with peers and caregivers helps them to form specific ideas about what is safe and why.