BioGnost’s P.A.S. Diastase kit is most commonly used for identifying glycogen in liver. Periodic acid enables the molecules containing glycol groups to create aldehydes affected by Schiff’s reagent staining them violet (magenta). Specific stains are created by applying the PAS method on unsubsti-tuted polysaccharides, mucoproteins and glycoproteins, glycolipids and phospholipids. Alpha-amylase enzyme (also known as diastasis) is used for differentiation between glycogen and other PAS-positive structures by dissolving 1→4 glycosidic bonds, causing the glycogen to remain unstained after the PAS reaction. BioGnost’s P.A.S. Diastase kit uses thermostable enzyme which does not require heating to +37°C to be active, but incubat-ing the section at +37°C is preferred in order to achieve better glycogen breakdown. The same tissue section is used as negative control for this reaction, but the sample is not treated using alpha-amylase.