This volume explores the key developmental transitions that take place as 1- to 3-year-olds leave infancy behind and begin to develop the social and emotional knowledge, skills, and regulatory abilities of early childhood. Leading investigators examine the multiple interacting factors that lead to socioemotional competence in this pivotal period, covering both typical and atypical development. Presented is innovative research that has yielded compelling insights into toddlers’ relationships, emotions, play, communication, prosocial behavior, self-control, autonomy, and attempts to understand themselves and others. The final chapter presents a systematic framework for socioemotional assessment. This book will be important reading for developmental psychologists; early childhood education researchers and professionals; students in these areas. It is also of interest to mental health clinicians working with young children and their families. It will also serve as a text in graduate-level courses in social development or early childhood development.