TB Stains are use to identify acid fast bacilli (Mycobacterium tuberculosis) in smears and tissue sections. The cell walls of Mycobacteria are not readily penetrated by aniline dyes solutions so in order to stain Mycobacteria the stain incorporates Basic Fuchsin (a red dye) and phenol to make a powerful stain. Heat can be applied to “force “the stain into the bacillus (standard Ziehl-Neelsen method). Once stained the bacillus is very resistant to decol ourisation retaining the stain even when the rest of the preparation has been decolourised. The contrast stain(s) used following the bacillus staining are weak solutions of either Methylene Blue or Malachite Green to give a pale blue or green background against which the stained(red) bacilli will be easily visible.