This chapter describes how the distributed cognition perspective directs attention to particular classes of interactions. It uses the examination of an example of real-world human interaction to construct a description of the nature of interaction. The chapter shows real-world interaction to be deeply multimodal and composed of a complex network of relationships among resources. It also shows that some cognitive processes are properties of the system of interaction, distinct from the cognitive properties of the individuals who participate in the system. Humans inhabit a cognitive ecology that contains many sorts of cognitive resources. Some of these are physical objects, some are cultural practices, and some are mental models. Cognitive effects emerge from the interaction of persons with the rich cultural content of the cognitive ecology. The individual and institutional knowledge of ship’s position is produced by the activity of a complex system involving interaction among persons and complex culturally organized material media.