Cover legend: The activated olfactory glomerulus and its functional compartments. The global activation of the olfactory glomerulus can be monitored through the imaging signals of associated metabolic responses, such as increased blood flow and glucose uptake (represented by the outer red glow in this figure). But what happens "behind the scenes"? Are all functional elements of the glomerulus equal in their contribution to the additional energy demands, or are there a few main players whose activity drives the metabolic response signal? A theoretical analysis of the glomerular energy budget suggests the latter. Glomerular energy consumption among the functional compartments is asymmetric. These compartments include the convergent olfactory receptor nerve axons and their presynaptic terminals (pink), the postsynaptic dendritic tufts of mitral (dark blue), tufted (light blue), and periglomerular (violet) cells, and the network of glial elements (gray/translucent). For more information, see the article by Nawroth et al. in the September 5, 2007 issue (pages 9790–9800).