at least 10 kpa e g from 10 to 50 kpa is applied more typically a pressure of from 13 to 40 kpa is applied the apparatus may further include means to measure electrophysiological or chemical signals which may be generated by a cell or biological surface and stimulated by the applied pressure such measurement means is conventional in sicm the basic arrangement of an sicm for topographical imaging of living cells has been described previously korchev et al biophys j 1997a 73 653 8 korchev et al j microsc 1997b 188 pt 1 17 23 briefly the sicm uses a patch clamp nanopipette arranged perpendicularly to the sample as a scanning probe the pipette is mounted on a three axis piezo translation stage in a traditional line scanning mode the probe approaches the cell surface and scans over it while maintaining a constant tip sample separation distance using the sicm feedback control that keeps the ion current through the pipette constant the sicm controller produces a surface image of the cell and makes possible a straightforward pipette approach precisely over an identified specific area or structure of the cell to within approximately 100 nm from the cell membrane whilst traditional line scanning scim can be used in both contact and non contact modes the contact approach can be of limited use in cell.