We present evidence for a previously unrecognized differential staining effect of Giemsa solution in fluorescence microscopy. The effect consists of selective fluorescent staining of mineralized bone (and elastic fibers) in tissue sections and, like the classical Romanowsky effect, is based on the differential binding of Eosin Y to tissue structures in the presence of Azur II and Methylene Blue. This effect opens the way to new applications of the Giemsa solution in fluorescence microscopy and in confocal fluorescence microscopy.