A device for performing cell assays has at least one assay site. The site comprises a pair of stimulating electrodes and a cell confinement cavity for confining at least one cell in an extracellular fluid medium. The cell confinement cavity and the stimulating electrodes are arranged so that, in use, each cell is exposable to an electrical field generated by a potential difference applied across the stimulating electrodes. The stimulating electrodes are spaced a distance apart such that the potential difference can induce field stimulation of each cell and simultaneously be below the level that would result in electrolysis of the extracellular fluid medium.