The innocence of childhood does not protect against exposure to stress. More than half of US children are exposed to adverse experiences, such as abuse, neglect, witnessing domestic violence, parental psychopathology, or divorce, and all children encounter normative stressors like school transitions and challenges with peers. This Element discusses research on stress psychobiology during childhood, from birth to age ten. The Element focuses on important contexts that shape children's responses to stress and their coping capacities, including the family system, peers, schools, neighborhoods, the broader culture, as well as clinical settings. Sources of stress and resilience in each context are described.