In psychotherapy, working with personality parts is becoming increasingly important. This introduction provides a compact overview of common models of parts and addresses their fundamental assumptions, peculiarities, and differences. Helmut Riessbeck combines psychoanalytic, behavioral, and hypnotherapeutic concepts into a coherent therapy for communication between personality parts. This culminates in a logical, transparent therapeutic process that offers patients with more severe impairments both support and room for change. Dissociative processes and reflexively automated behaviors become transparent and accessible in new ways for both the therapist and the patient. Brief theoretical sections are illustrated with therapeutic exercises, the presentation of specific techniques, and expert knowledge.