Our basic problem in this research has been to characterize and explain the growth or development of social systems. To this end we have attempted to apply in two separate structural contexts-the industry and the family-a model of differentiation which posits a typical sequence of events which occurs when the system increases in complexity. The sequence begins when members of the system in question (or some larger system) express dissatisfaction with some aspect of the system's functioning (Step 1). This dissatisfaction may concern role-performance in the system, the utilization of its resources, or both. In either case the dominant values governing the system legitimize the expression of the initial dissatisfaction. Accompanying the dissatisfaction, furthermore, is the prospect of facilities to overcome the source of dissatisfaction. The immediate responses to the dissatisfactions (Step 2) are undirected or misdirected symptoms of disturbance-phantasy, aggression, and anxiety. Even though non-specific with regard to concrete methods of overcoming the dissatisfactions, these symptoms are related symbolically to the original foci of dissatisfaction. Gradually these disturbances are brought into line by mechanisms of social control (Step 3), and their energy turned to the generation of more specific solutions for the original problems giving rise to the dissatisfactions. In this way future lines of action are encouraged (Step 4), specified (Step 5), and tried (Step 6). The social units which emerge, if the sequence is successful, constitute a structure more differentiated than the old. The new units, being more specialized, function more effectively than the old. Finally, after a period of extraordinary progress, the new units are consolidated into the social system and thereby routinized (Step 7).