Dimidium bromide is used as a fluorescent stain in biological and parasitological research, particularly for visualizing DNA in protozoa, bacteria, and certain animal cells. It binds to DNA and emits bright green fluorescence when excited by UV light, enabling clear observation of nuclear structures or chromatin under fluorescence microscopy. Commonly applied in detecting parasitic infections, such as trypanosomes, in biological samples like blood or tissue. Also used in studies of bacteria and protozoa. Requires careful handling due to potential toxicity.