Abstract
This chapter views attention as an organ system consisting of three brain networks with their own unique anatomy, connectivity, neuromodulators, and functions. These networks underlie the functions of attention including: obtaining and maintaining the alert state, orienting to sensory events, and voluntary control of responses. It traces the development of these attentional networks from infancy to adulthood. All three networks are present in infancy, but their functions and connectivity change in development. The change of control from the orienting to the executive network that takes place between infancy and childhood underlies the increasing role of voluntary control of emotions and thoughts. It examines how genes and environment influence this development and suggests avenues for further understanding of how attention develops.