This research brief from the National Commission on Social, Emotional, and Academic Development explores how emotions and relationships drive learning and are a fundamental part of how our brains develop. Authors Mary Helen Immordino-Yang, a professor of education, psychology and neuroscience at the University of Southern California and a member of the Council of Distinguished Scientists, and Linda Darling-Hammond, the president and CEO of the Learning Policy Institute and a co-chair of the Commission, explain how emotionally safe and cognitively stimulating environments contribute to brain development; how brain development that supports learning depends on social experiences; and how sensitive periods in brain development align with opportunities for learning and needed supports.