The brain has always been a bit mysterious. How does it all work so that a human being can live, breathe and talk. The brain is composed of two broad classes of cells: neurons and glia. These two types are equally numerous in the brain as a whole, although glial cells outnumber neurons roughly 4 to 1 in the cerebral cortex. Glia come in several types, which perform a number of critical functions, including structural support, metabolic support, insulation, and guidance of development. Astrocytes (brain cells named after their characteristic star-shape) that were previously thought to act only as the glue between neurons have a central role in the regulation of breathing.