This textbook provides detailed information on the current state of group psychology. Through numerous practical exercises and experiments, readers are encouraged to experience the content themselves. The described exercises have been tested in many seminars and serve as proven training material for instructors, behavior trainers, and facilitators. The theme-centered interaction serves as an integrative reference system for implementing the individual insights. Additional practical examples such as conversation management and motivation, peer consultation, and social competence training illustrate how theoretical aspects can be concretely applied in working with groups. Furthermore, the influence of the internet on social learning processes is discussed.