This proposal will result in the development of a new type of optical microscope, specifically designed to image biological materials, by utilizing the very recent technology referred to as photon scanning tunneling microscopy (PSTM). This new microscope will provide three- dimensional topographical images of biological and medical samples in liquid environments with a resolution an order of magnitude better than that possible with the best conventional optical microscopes. It will make possible the examination of living organisms in buffered solutions with a resolution approaching that of scanning electron microscopes without the elaborate sample preparation techniques required by electron microscopy. The proposed instrument will be designed to allow rapid examination of conventionally prepared biological samples on standard microscope slides. Furthermore, the new microscope would possess the inherent spectroscopic capabilities of chemical mapping of the sample with sub-wavelength resolution. During Phase I of this project we will design and construct a PSTM head which can be mounted on the rotating turret of a conventional microscope and will be able to operate in a liquid environment. We will demonstrate that this instrument can operate reliably with excellent signal to noise characteristics while imaging biologically important samples. During Phase II we will design and construct a cost effective working PSTM prototype with the reliability and ease of use such as to make it suitable for commercial production. Phase III involves commercialization of this patented technology through fabrication, marketing and sales of various stand-alone instruments based on this technology.