This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book covers various stages in my attempts to solve the problem represented by the fact that, though group dynamics are different from the dynamics of individuals, yet group is often defined as the sum of individual dynamics. It offers a solution, which was to suggest “role” as an intervening variable between individuals and groups. The book summarizes the practice of systems-centered therapy, which provides a systems language that applies to individuals, groups, organizations, nations, and so on. It focuses on the differences between group-as-a-whole approach and the group-as-a-whole traditions that had emerged from the work of Bion and the Tavistock. The book compares developing theory with Foulkes’s theory for group analysis. It presents a further step in observing group dynamics through the frame of subgrouping.