This paper further develops a new theory of power advanced by the authors in two previous papers (Galam and Moscovici, 1991, 1994). According to this theory power results from the build up of conflicts within a group, these conflicts requiring a degree of organizational complexity which is itselfa decreasing function of group size. Within this approach, power appears to be a composite of three qualitatively different powers, institutional, generative and ecological. Levels and relationships among these forms of power are considered as a function of the diversity of the group. There exist also three states of organization associated with power evolution. At the group initial stage is the paradigmatic state. Creation and inclusion of conflicts are accomplished in the transitional state through the building of complexity. At a critical value of diversity, the group moves into the agonal state in which institutional power vanishes simultaneously with the fusion of generative and ecological powers.