BioGnost’s Hematoxylin ML is one of the formulations of hematoxylin used in histopathology and cytology for a more precise nuclear cell staining. It is applied both progressively and regressively in a routine hematoxylin and eosin (HE) staining and counterstaining in immunohistochemistry. Hematoxylin is extracted from logwood (Haematoxylon campechianum L.). Hematoxylin oxidizes to hematein and binds with metal ions (mordants), hematein turns into irreplaceable nuclear color. Positively charged hematein-mordant complex then binds with negatively charged phosphate ions of the DNA’s nucleus, creating characteristic blue coloration. Unlike the hematoxylin acc. to Mayer, modified hematoxylin acc. to Mayer-Lillie contains 5 times greater concentration of hematoxylin, it is glycerol-stabilized, and a low pH value contributes to strong selectivity of color coding according to chromatin. By using the progressive method of staining, the microscopic samples are exposed to modified hematoxylin acc. to Mayer-Lillie long enough to stain the nucleus only, while regressive staining can also dye mucin (as well as the nucleus). BioGnost’s Hematoxylin ML provides outstanding results in staining the nuclear membrane, nucleoplasm, nucleolus and mucin if the regressive method is used.