Temperament refers to early-appearing variations in emotional reactivity and regulation that show moderate stability across time and settings. The association of some features of early temperament with later emerging childhood psychiatric disorders has been well established. For example, a temperamental predisposition toward experiencing increased negative affect in the presence of novelty during early childhood has been linked to later anxiety disorders.¹ Accumulating research directed at understanding the mechanistic links between temperament and psychopathology indicates that, at least for most disorders, the 2 constructs cannot be viewed as simply different points along a shared continuum. That is, temperament as a risk factor for psychopathology has been suggested to depend on a number of other internal as well as external factors,² and these factors likely exert their influence at least in part by shaping the early course of brain development.³ However, until recently, the associations between very early features of temperament and brain development have remained relatively understudied owing to the practical and technical challenges of using neuroimaging techniques such as functional magnetic resonance imaging during this highly sensitive developmental period. Nevertheless, with advances in each of these areas, early functional magnetic resonance imaging evidence is beginning to provide an exciting new window into these relationships.