apparatus is provided for investigating surface structures irrespective of the materials involved . a fine scanning tip is heated to a steady state temperature at a location remote from the structure to be investigated . thereupon , the scanning tip is moved to a position proximate to , but spaced from the structure . at the proximate position , the temperature variation from the steady state temperature is detected . the scanning tip is scanned across the surface sturcture with the aforesaid temperature variation maintained constant . piezo electric drivers move the scanning tip both transversely of , and parallel to , the surface structure . feedback control assures the proper transverse positioning of the scanning tip and voltages thereby generated replicate the surface structure to be investigated .