Cover legend: Confocal micrograph of the vasculature of the rat retina, labeled for the pericyte marker NG2 (green), the contractile protein α-smooth muscle actin (red), and the vessel marker Isolectin-IB4 (blue). A primary arteriole (left) branches into smaller arterioles and capillaries. A primary venule is at the right. Retinal blood flow is actively regulated primarily by dilation and constriction of the larger arterioles. For more information, see the article by Kornfield and Newman (pages 11504–11513).