The legacy of the last century of research in psychiatry has been the sophisticated understanding of the role of neuronal systems in brain function and ultimately in psychopathology. As a consequence, an armamentarium of drugs to treat neuropsychiatric disorders has been developed that work by altering chemical neurotransmission in the brain. Curiously, little attention has been paid to the nonneuronal cellular components of the brain, which outnumber neurons by a factor of 10.1 Glia, a heterogeneous population of cells, have largely been viewed as passive handmaidens to the neurons, which have been considered the primary arbiters of information processing in the brain. The term glia, which means glue in German, was first applied to these cells by Virchow2 in a psychiatric report more than 150 years ago.