Microglia were recently shown to play unexpected roles in normal brain development and adult physiology. This has begun to dramatically change our view of these resident “immune” cells. Here, we briefly review topics covered in our 2011 Society for Neuroscience minisymposium “The Role of Microglia in the Healthy Brain.” This summary is not meant to be a comprehensive review of microglia physiology, but rather to share new results and stimulate further research into the cellular and molecular mechanisms by which microglia influence postnatal development, adult neuronal plasticity, and circuit function.