Localised electrochemical impedance system allows spatially resolved impedance measurements to be made. It combines the principles of EIS measurements with scanning probe technology. A small sinusoidal voltage or current perturbation is applied to a working electrode sample and the resulting current is measured to allow the calculation of the impedance. However, rather than measure the bulk current, a small electrochemical probe is scanned close to the surface, measuring the local current in the electrolyte.