Long thought to be the brains janitorial staff, sopping up excess transmitter and turning up the blood supply when the neurons complained, Astrocytes are now known to be doing something of great importance for cognition.Exactly what they are doing is not clear because they are exceedingly hard to study. In my talk I will explain why they are thought to be so important, what kinds of things they do and why it could be vital for cognition. There is no computational theory yet, but one is needed and the theoretician who comes up with on might get a good job some day.