Crystal Violet is the primary stain used in the Gram's Staining method. Crystal Violet is used in the identification of Gram Positive and Gram Negative organisms. Positive organisms have a thick cell wall and resist alcohol decolorization leaving the cells stained a purplish-blue color. Negative organisms have thinner cell walls, causing the Crystal Violet to wash out during the alcohol decoloration. FDA approved for in vitro diagnostic use.