Résumé : The coupling between electrochemistry and fluorescence confocal laser scanning microscopy (FCLSM)allows deciphering the electrochemical and/or redox reactivity of electroactive fluorophores. This isdemonstrated with phenoxazine electrofluorogenic species frequently used in bioassays by mapping thevariation of fluorescence intensity with respect to the distance from the electrode. The electrochemicalconversion of resorufin dye (RF) to non-fluorescent dihydroresorufin (DH) leads to a sharp decrease ofthe fluorescence signal in the vicinity of the electrode. In contrast, the direct reduction of resazurin (RZ)to DH leads to an unexpected maximum fluorescence intensity localized further away from the surface.This observation indicates that the initial electron transfer (heterogeneous) is followed by a chemicalcomproportionation step (homogeneous), leading to the formation of RF within the diffusion layer witha characteristic concentration profile. Therefore, in situ FCLSM affords a direct way to monitor suchchemical reactivity in space and to decipher a new redox pathway that cannot be resolved solely byelectrochemical means.