Recent scientific findings and experiences regarding children's and youth training, as well as current sports policy guidelines on the structures of youth training, have prompted the authors to create this handbook. It addresses three main areas: Part I covers the developmental characteristics of children and adolescents, athletic performance and trainability, as well as sports talent. Part II is a practical-conceptual training theory that includes training principles, long-term performance development, management and planning, as well as training content and methods. Part III describes competitions for children and adolescents and the organizational and support structure of a youth training system.