Research over the past several decades has provided insight into the processes that govern early brain development and how those processes contribute to behavior. In this article, the authors provide an overview of early brain development beginning with a summary of the prenatal period. They then turn to postnatal development and examine how brain functions are built and how experience mediates this process. Specifically, they discuss findings from research on speech and on face processing. The results of this research highlight how the first few years of life are a particularly important period of development of the brain.