Histology, cytology and other related scientific disciplines study the microscopic anatomy of tissues and cells. In order to demonstrate a good tissue and cellular structure, the samples need to be stained in a correct manner. Sudan IV is a lipophilic diazo dye, very similar to Sudan III. It is primarily used in the Sudan IV staining method or in Churukian’s variety of Lillie-Ashburn method in which it replaces Oil Red O. Those methods are used for staining lipids, triglycerides and lipoproteins on frozen histology sections. They are also used for identifying the outer lipid sheath of pollen grains and for the identification of liquid fats in food.