An expanding number of molecules have been reported to have luminescent properties directly related to their redox state. Coupling the luminescence of these molecules to the electrochemistry of interest, either directly or indirectly, is becoming increasingly popular for visualisation of electrode processes. Luminescence induced by direct electron transfer can reveal the heterogeneity of an electrode and allow the activity of the electrode to be spatially resolved in situations where current can only give an averaged view of activity. An example of a fluorophore used to directly couple to electrochemistry is resorufin, a molecule which can be generated by the oxidation of the non-fluorescent dihydroresorufin molecule (or its non-fluorescent derivative Amplex Red (AR), see Scheme 1) or by the reduction of the less fluorescent resazurin molecule. The electrochemical generation of this molecule has been studied using confocal fluorescence microscopy, providing information about its reaction mechanism and the thickness of its diffusion layer. In another example, the 5-cyano-2,3-di(p-tolyl)tetra-zolium chloride fluorophore was irreversibly deposited into the gaps of an insulating TiO 2 layer on top of a microelectrode, revealing fluorescent islands which were used to map out the defects sites of the TiO 2 layer. In a demonstration of increased sensitivity and temporal resolution, the fluorescence of Nile Red was recently used to detect the impact of attoliter droplets of toluene emulsions on a carbon fibre electrode. The electrochemiluminescence of tris(bipyridine) ruthenium(II) ([Ru(bpy) 3 ] 2+ ) has also been used to indicate the distribution of potential in a bipolar electrochemical cell and and observe the real-time passivation of silicon surfaces. Luminescence induced by indirect electron transfer can reveal changes in local stimuli and uncover the kinetics of the electron transfer. Confocal fluorescence microscopy of the pH-sensitive fluorescein molecule has been used for 3-dimensional mapping of the proton gradient at a microelectrode and for evaluation of the number of electrons passed during the oxygen reduction reaction Another pH-sensitive fluorophore, 8-hydoxypyrene-1,3,6-trisulfonic acid (HPTS), has been used to study the reaction layer of p-benzoquinone reduction around a carbon fibre inside a thin-layer cell. Recently, the concept of electrochemically induced luminescence has been applied to remotely report on electrochemistry occurring in a separate cell.