Two-photon image displaying interactions between astrocytes and cerebral blood vessels in the barrel cortex of an awake mouse. Blood vessels (red) were visualized with rhodamine dextran. During whisker stimulation and arteriole dilation, astrocytes exhibited activity-dependent fluorescence via a genetically encoded calcium indicator. Fluorescence changes are pseudo-colored to represent the transition from a resting (blue) to an activated state (green). Compared to wild-type mice, astrocytes in an Alzheimer's disease mouse model were hyperreactive, but also less sensitive to blood vessel contractions and dilations. See the article by Blaine Weiss et al. for more information. Cover image: Blaine Weiss