Hay integrates the approaches of classic developmental differentiation and differential emotions theory to create a comprehensive textbook with a unique approach to the subject matter, showcasing a range of research linking emotions to biological underpinnings and early experiences. This wide-ranging book also includes coverage of differences in temperament, developmental psychopathology, emotion regulation and development of emotional understanding, and attachment. It is core reading for students of developmental psychology, health psychology, child welfare and social work, as well as anyone taking a course on social and emotional development courses. It will also be of interest to practitioners working in educational and clinical psychology and child psychiatry.