Perls Prussian blue is a commonly used method in histology, histopathology, and clinical pathology to detect the presence of iron in tissue or cell samples.[1][2][3][4] Perls Prussian Blue derives its name from the German pathologist Max Perls (1843–1881), who described the technique in 1867.[2] The method does not involve the application of a dye, but rather causes the pigment Prussian blue to form directly within the tissue.[5] The method stains mostly iron in the ferric state which includes ferritin and hemosiderin, rather than iron in the ferrous state.[6]