This PYI award is to improve thebasic understanding and the application of optical spectroscopy to biomedical problems. Fluorescence and reflectance spectroscopy are powerful techniques for analyzing the chemical composition of tissues noninvasively. As a first step, the PI will analyze the information contained in a fluorescence spectrum from a multi-component, scattering tissue. Using imaging techniques, methods will be developed for characterizing the tissue as a function of position within the sample. It is expected that the proposed research will significantly enhance the treatment of diseases (such as atherosclerosis and neoplasia) where a quantitative understanding of tissue composition is essential.