Adolescence is an extremely unique and critical stage of development. In order to provide the helping professional with a clear understanding of typical adolescent development, and to fill the gap many have in understanding adolescence in general, this book offers a concise, in-depth, scientific overview of adolescent development specifically geared toward those applying the information in the helping professions. The intended audience for the book is helping professionals such as psychologists, mental health counselors, social workers, marriage and family therapists, educators, and nurses. The book covers adolescent developmental theories that provide a basis for understanding observations about the nature of adolescents. These theories include the intrapsychic, cognitive, behavioral/environmental, and biological theories. Puberty is also the signal indicating the beginning of physical and neurological growth. The hormonal changes of puberty initiate drastic growth in the body and organs of adolescents. The book reviews several aspects of overall adolescent health, including the issue of adolescent sleep and its importance and how adolescent diet and nutrition impact development. In addition to the “hardware” transformation in an adolescent’s brain, adolescents undergo important changes in their ability to think. The book also examines Piaget’s adolescent stage of cognitive development, the formal operational stage, and how changes in the way adolescents think impact their interactions with others. It introduces the multiple social changes with family and friends that occur during adolescence and examines how adolescents interact with TV, media, and technology and deals with the issue of cyberbullying and reviews the most common adolescent problems, such as drug use, risky behaviors, eating issues, and depression. Each chapter integrates several features to guide helping professionals in applying adolescent development in practice.