1. A method for detecting chemical differences between a cell sample and a reference cell sample, utilizing single-cell infrared microspectroscopy, said method comprising: (a) directing a beam of infrared light through an aperture of approximately single cell size at single cells in a cell sample to produce absorption data for each of said single cells; (b) comparing said absorption data for each of said single cells with infrared absorption data acquired from individual cells in at least one reference cell sample to provide comparison data for each of said single cells in said cell sample; (c) generating scores for said absorption data using said comparison data; (d) creating frequency distribution profiles from said scores; and (e) detecting said chemical differences using said frequency distribution profiles.