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Summary form only given. Confocal laser scanning microscopy (CLSM) provides a significant improvement in axial resolution over conventional epi-fluorescence microscopy by eliminating out-of-focus fluorescence. This is achieved by using a spatial filter in the form of a confocal aperture. The use of IR leads to a larger penetration depth in materials, providing an opportunity to image thicker samples. Furthermore, it is possible to open up the entire visible spectrum for multiple detection channels. The fluorophore, 4-[N-(2-hydroxyethyl-N-methyl) amino phenyl]-4'-(6-hydroxyhexyl sulfonyl)stilbene (APSS), exhibits a strong two-photon absorption at 800 nm, and green upconverted fluorescence emission.