To identify the unknown organism, we first need to obtain a pure culture of the organism. Once the pure culture is obtained, it can be subjected to Gram staining. • Gram Staining is done to differentiate bacteria into two groups based on the difference in their cell wall composition. Two dyes, namely, crystal violet (primary stain) and safranine (counterstain), are used along with iodine (as a mordant) and 70% ethanol (as decolourizing agent). The cell wall of Gram-negative bacteria contains large amounts of lipids. When the decolourizing agent is used, the violet color is removed from the cell wall of Gram-negative cells. When viewed under the microscope, Gram-positive organisms appear purple while Gram-negative ones appear pink in color.