One of the most frequently used chemical methods in histology is P.A.S. staining. The P.A.S. staining is based on the oxidation reaction with the presence of periodic acid and Schiff’s reagent. Periodic acid makes the molecules containing glycol groups create aldehydes affected by Schiff’s reagent that stains them violet (magenta). This method is most commonly used in liver and muscle cells testing. Specific stains are created by applying P.A.S. method on unsubstituted polysaccharides, mucoproteins and glycoproteins, glycolipids and phospholipids. Combined with Alcian Blue, it can detect acid mucosubstances (glycosaminoglycans).