Perl's stain is used to demonstrate

(B) Haemosiderin > Hemosiderosis: With progressive accumulation of hemosiderin, parenchymal cells throughout the body (principally in the liver, pancreas, heart, & endocrine organs) become pigmented, iron can be visualized in tissues by the Prussian blue histochemical reaction, in which colorless potassium ferrocyanide is converted by iron to blue-black ferric ferrocyanide.> Perl's Prussian Blue Stain for Iron-Positive Cells (e.g., activated macrophages) (a.k.a. Perl's acid ferrocyanide reaction)