Sudan Black B stains lipids and phospholipids present in the cells. The positive reaction gives a brownish black color. The granulocytic precursors follow a pattern of sudanophilia and the granules of granulocytic cells stain positive in SBB. The stain is the most commonly employed cytochemistry procedure in differentiating AML from ALL, since Lymphoblasts and Lymphocytes stain negative with SBB. The SBB stain kits are commercially available. The whole procedure takes a little more than an hour.