This chapter discusses how coordination is essential to cognition and behavior. It begins with problems inherited from conventional cognitive science, for example the question of intentionality. Then, it discusses theoretical terms of complexity science that have proven useful in cognitive and behavioral science. They culminate in the ideas of self-organized criticality and soft-assembly: Living systems are attracted to optimal temporary states of flexible coordination, which best guarantees contextually appropriate behavior and the wellbeing of the actor. In addition, it describes the conceptual building blocks of complexity with respect to brains, bodies, and behavior. These include constraints, phase transitions, interdependence, and self-organized criticality-concepts that address emergent coordination among system components. Further, it discusses ubiquitous pink noise in human performance. Pink noise is a fundamentally complex phenomenon that reflects an optimal coordination among the components of person and task environment. Discussion concludes with a survey of present challenges and opportunities for complexity and cognitive science.