An apparatus is described which can make force vs. displacement measurements on regions of a living cell. A force on the order of 10−3dyne is applied by a stylus to an area of about 10 &mgr;m2on the upper side of a cell growing on a culture dish. The resulting deformation is deduced from a solution conductance measurement with a sensitivity of 0.1 &mgr;m. The technique is compatible with optical microscopy and electrophysiological recording.