Fig. 1. Ca²⁺ puffs in a HeLa cell. The black and red traces in A show the onset of a Ca²⁺ wave in a single histamine-stimulated HeLa cell. The Ca²⁺ puffs are visible prior to the Ca²⁺ wave. The spatial profile of a Ca²⁺ puff is indicated by the surface plot in B. Ca²⁺ concentration is coded by the height and colour of the surface. The black and red traces in A were obtained by averaging the Ca²⁺ concentration over the regions marked by the correspondingly coloured circles on the inset cell image. Modified figure reproduced, with permission, from Thomas et al., 2000.