How does a low-level multicellular organism coordinate its cells to achieve organism-level behaviours? We studied this process in the case of phototaxis (swimming towards the light) of the colonial green algae Volvox and we discovered that coordination is achieved by a common cellular response program to environmental stimuli, a precise morphological organization and a mutual 'fine-tuning' of the biochemical time scales with the characteristic spinning frequency of the colony in its viscous physical environment.