John Bowlby's work on attachment theory is considered a classic in psychology. His studies from the 1960s are groundbreaking and serve as a foundation for many more recent psychological research efforts. Attachment, which refers to the secure relationship with a mother, father, or another caregiver, is a fundamental human motivation. It shapes individuals well into adulthood and plays a significant role in the development of all subsequent relationships. In the volume "Loss," John Bowlby compares the reaction of a child who loses their caregiver to that of an adult whose partner or child has died. Bowlby illustrates through numerous case studies the factors that influence the grieving process in both children and adults. His research findings provide groundbreaking insights for anyone assisting individuals in coping with their traumas.