In this book, we have looked at some aspects commonly found in urban cities within developed countries. Although the chapters are all from Hong Kong (China's most international city) with a focus on Chinese children and adolescents, key developmental issues are reviewed and new research agenda are discussed with implications for other cultures and cities. This book might be of interest to researchers who want to develop a new framework for understanding some of the most intriguing developmental issues of today's youth. They may find new perspectives and precious hints for planning future research. In addition, teachers, psychologists, social workers, and mental health practitioners in general should also be interested, as they need to design prevention or intervention programs to reduce the risk factors for adolescents. Finally, we hope it may be a resource for everyone involved at any level with the promotion of positive youth development.