This book provides a comprehensive and accessible introduction to key concepts of attachment theory, from the work of its founder John Bowlby to the most recent research within the field. The first part of the book gives readers a clear understanding of attachment theory during infancy, childhood, adolescence, adulthood and in bereavement. The second part of the book illustrates how attachment theory can be used to inform clinical interventions with children in different contexts, adults, and within wider health, social and educational systems. Using case examples throughout, the authors provide the reader with a practical understanding of the clinical applications of attachment theory across the lifespan and in varying health, social care and educational systems. Attachment theory is one of the most important lifespan development theories and is relevant to students and practitioners from a wide range of disciplines, including medicine, nursing, psychology, child development, mental health and applied social sciences.