The present disclosure is directed to an improved method for distinguishing tissue from an embedding medium, such as paraffin in a formalin-fixed paraffin-embedded sample. The method involves the use of fluorescence of naturally-occurring species in tissue to determine the location of the tissue in the embedded sample. An embedded sample is generally excited by light of a selected wavelength, and the fluorescence emission at an emitted wavelength is used to locate the boundary or location of the tissue in the embedded sample.