1. A process for intra-operatively identifying a parathyroid tissue of a living subject, comprising the steps of: (a) illuminating, with a light, source, tissues in the neck area of the living subject with a beam of light having a predetermined wavelength; (b) obtaining, with a detector, auto-fluorescence spectra of intensity from light emitted from the illuminated tissues in the neck area, wherein each auto-fluorescence spectrum is corresponding to a region of the neck area whose tissue emits auto-fluorescence light in response to the illumination, wherein the predetermined wavelength is adapted such that the auto-fluorescence spectra of intensity of the light emitted from the illuminated tissues in the neck area are in a wavelength range of 800-1000 nm; (c) identifying, with a controller, one of the auto-fluorescence spectra having a highest peak intensity among the auto-fluorescence spectra; and (d) identifying, with the controller, the tissue of the region of the neck area that corresponds to the one of the auto-fluorescence spectra having the highest peak intensity as the parathyroid tissue.