Confocal laser scanning microscopy was used in, situ during electrochemical experiments to track localized fluorescence patterns of adsorbed organic agents and to correlate such adsorption with changes in surface morphology accompanying electrolysis. In solutions of 5 mu M DiOC(6)(3)/0.01 M H2SO4, with and without 0.05 M CuSO4, confocal imaging revealed that DiOC(6)(3) adsorbed to polycrystalline Au and inhibited cathodic processes occurring there. In the absence of dissolved Cu, DiOC(6)(3) adsorption on Au remained unaltered by changes in cathodic potential up to -750 mV (SSE). During Cu electrodeposition at -550 and at -650 mV (SSE), adsorbed DiOC(6)(3) restricted nucleation of Cu to a small number of active sites where Cu grew hemispherically; and DiOC(6)(3) adsorption was maintained across regions where nucleation had not occurred. Instantaneous nucleation was approached under such conditions. When DiOC,(3) was present, copper growth proceeded according to the Volmer-Weber mechanism at -650 mV (SSE). Results from secondary ion mass spectrometry indicated that DiOC(6)(3), or a derivative of it, was incorporated into the deposit during Cu electrode-position. During electrodissolution of Cu on Au at 0 mV (SSE), adsorption of DiOC(6)(3) occurred predominantly at surface sites of Cu rather than Au.