Parental sensitivity and nurturance are important mechanisms for establishing biological, emotional, and social functioning in childhood. Sensitive, nurturing care is most critical during the first three years of life, when attachment relationships form and parental care shapes foundational neural and physiological systems, with lifelong consequences. Sensitive, nurturing care also buffers children from the negative effects of growing up in difficult circumstances such as poverty. In this article, Carrie DePasquale and Megan Gunnar examine several interventions that directly or indirectly target parental sensitivity and nurturance, and demonstrate the causal role that this type of care plays in children's development, especially during the first three years of life. They note that even though sensitive, nurturing care is still helpful after infancy and early childhood, it doesn't completely mitigate the effects of not receiving this type of care early in life. And because sensitive care involves knowing when to respond and when to let the child manage more independently, excessive responsiveness, overinvolvement, and intrusiveness are also forms of insensitive care. Sensitive and nurturing parent behaviors vary across cultures, and numerous other factors influence parental sensitivity as well. For example, children's temperament and emotional reactivity may affect parents' behavior and/or alter the effects of parenting behavior on children's development. Physiological, cognitive, and emotional self-regulatory capabilities, as well as socioeconomic and environmental factors, can also affect a parent's ability to provide sensitive, nurturing care. Based on the expansive research related to parental sensitivity and nurturance, the authors recommend that policy makers should aim to increase family and community access to programs that enhance sensitive, nurturing care and support parents so they can provide high-quality care to their children.