Sudan IV is a bis(azo) compound that is 2-naphthol substituted at position 1 by a {2-methyl-4-[(2-methylphenyl)diazenyl]phenyl}diazenyl group. A fat-soluble dye predominantly used for demonstrating triglycerides in frozen sections, but which may also stain some protein bound lipids in paraffin sections. It has a role as a carcinogenic agent, a fluorochrome and a histological dye. It is a member of azobenzenes, a member of naphthols and a bis(azo) compound. It is functionally related to a 2-naphthol.