This chapter takes a more dynamic approach, looking at activities as the basis on which social scientists build the information they use to analytically construct processes designated as actions, interactions, practices or behaviors. Processes can vary greatly in length and scope. Some can be broken down into interrelated sub-processes, sometimes referred to as sequences. The way in which persons view current or future activities varies according to the degree of uncertainty they associate with these activities and the consequences they anticipate. A typology based on these two criteria makes it possible to define “activity regimes”. Analyzed a posteriori, a process can be characterized by the forms of unpredictability it brings into play and by the consequences it entails. Articulating these two aspects enables us to rediscover classic social science analytical schemes (reproduction of an equilibrium, gradual change, bifurcative change).