In-situ imaging of electrochemistry of individual, micrometer-sized Pt clusters supported on glassy carbon is described. The image is formed by the local current change induced by the local temperature transient caused by a scanned, focussed laser. A confocal scanning laser microscope was adapted for this purpose. Differences in electrochemical activity, and differences in electrochemical behaviour of the individual clusters, are demonstrated. In principle, electroactive particles of nm size on a support where the electrochemistry is irreversible can be detected and characterised. The advantage of the method is that it allows relatively large areas to be scanned quickly, with a simple zoom into any area of interest. It is usefully complementary to scanning probe microscopy.