Astrocytes can drive the master clock in the brain The neurons of the suprachiasmatic nucleus (SCN) of the hypothalamus function as a central circadian clock, coordinating mammalian physiology with the 24-hour light-dark cycle. Brancaccio et al. found that these neurons have help from neighboring astrocytes (see the Perspective by Green). In mice lacking the Cry gene, which encodes a critical clock component, restoration of Cry expression and molecular clock function in the astrocytes, but not the neighboring neurons, restored rhythmic transcriptional oscillations in the SCN and reestablished circadian behaviors in the mice. Science , this issue p. 187 ; see also p. 124