This article looks at what influences a child’s ability to be resilient and how supportive caregiver relationships are key to children’s positive development outcomes. Science shows that children who do well despite serious hardship have had at least one stable and committed relationship with a supportive adult. These relationships buffer children from developmental disruption and help them develop “resilience,” or the set of skills needed to respond to adversity and thrive. This working paper explains how protective factors in a child’s social environment and body interact to produce resilience, and discusses strategies that promote healthy development in the face of trauma.