Sudan Black B stain is intended for the visualization of lipids. Black Sudan B is used for the staining of a wide variety of lipids such as phospholipids, steroles and neutral triglycerides. Black Sudan B is not lipid specific like other Sudan dyes and can also be used for chromosome staining, Golgi apparatus and leukocyte granules.

The dyes of the Sudan family form a group of solvent-soluble lipid dyes. They are called lysochromes and in the structural classification they are diazo dyes.

Black Sudan B is used in the study of hematological pathologies because it is able to stain myeloblasts and not lymphoblasts.

Normal granulocyte precursors show increased sudanophilia which corresponds approximately to the number of granules. Promyelocytes contain some sudanophilic granules and mature neutrophils contain a large number of sudanophilic granules. Eosinophilic granules are also sudanophilic, especially at the edge. Monocytes may not be colored or may contain some discrete sudanophilic granules. Macrophages often contain sudanophilic material.