Sudan Black B works also in frozen material, and therefore can be complementarily used with SA-β-gal when investigating senescence. Sudan Black B is a highly lipophilic agent that exhibits high affi nity to the lipid compartment of lipofuscin. The positive Sudan Black B-lipofuscin reaction reveals blue-black intracellular granules in cells and frozen tissues and brown to black granules in FFPE tissues under the light microscope.