Focusing on the emergence of gender difference as a major life transition, this study provides a summary of interdisciplinary research that includes contributions from an international team of leading experts. Puberty is one of the most important life transitions. At no other time are there such significant and rapid transformations in biology and social and psychological development. Topics covered in this volume include biological aspects of puberty, body image, aggression, sexual abuse, opposite-sex relationships and the psychopathology of puberty.