Power is a core dimension of social interactions and relationships. The present article addresses how power hierarchies form, how power is expressed and perceived via verbal and nonverbal behaviour during social interactions, and whether power of others can accurately be assessed. Taking into account the inherently relational and interactional nature of the power concept, an interpersonal power and behaviour model is presented. The model explicitly differentiates between different facets of power (status, position power, personality dominance, competence, experienced power, and perceived power) and it is suggested that these facets can moderate the power-behaviour link. Research evidence is provided to illustrate the importance of a refined view of the concept of power and of integrating the different power facets in theorizing about power.