The term flow originates from studies on what motivates people to devote more time to activities – across both work and play settings – than could be expected based on external rewards such as money or fame. The main underlying reason appears to be the intrinsically rewarding subjective experience of flow. Flow refers to a psychological state of high but subjectively effortless attention, low self–awareness, sense of control and enjoyment that can occur during the performance of tasks that are challenging but matched in difficulty to the skill level of the person. This chapter gives an introduction to flow that focuses on the prerequisites and phenomenology of effortless attention, and how the flow experience relates to perception, cognition, and action. Flow and creativity are discussed in particular detail, centering on three hypotheses of how flow may relate to creative cognition; as a motivating factor for task engagement and skill acquisition, as a feedback signal for optimal task-based adaptation, and as relying on similar psychological and neural underpinnings. Lastly, the need for more basic research and applied research is discussed – the former on the relation between flow states and the quality of creative performance and the latter on how the concept of flow could be implemented successfully in training and education.