1-(2-(4-(2-(2,5-Dimethylphenyl)diazenyl)-2,5-dimethylphenyl)diazenyl)-2-naphthalenol

Oil red O is a fat-soluble bis(azo) dye, specifically a 2-naphthol derivative substituted with arylazo groups. It is predominantly used as a histological dye for demonstrating triglycerides in frozen tissue sections and for staining protein-bound lipids in paraffin sections.