Twenty Years of Calcium Imaging: Cell Physiology to Dye For

Confocal image of a rat mesenteric small artery loaded with a Ca²⁺-sensitive dye. The horizontal streaks are smooth muscle cells with an overlaying network of sympathetic nerve fibers. The graph shows a time series of three smooth muscle cells. The Ca²⁺ oscillations are first unsynchronized and later synchronized. The scale bar is 4 μm. (Image kindly provided by Christian Aalkjaer, University of Aarhus, Denmark.)