The Gram staining is one of the oldest and most important staining techniques used in microbiology first introduced in 1882 by Hans Christian Gram. The staining is the most crucial staining in microbiology and is the first step in differentiating bacteria. The gram-positive bacteria have thick cell wall because of thick layers of peptidoglycan, thus stain purple whereas gram-negative bacteria have thin layers of peptidoglycan and stains red/pink. Decolonization is most important step in gram sta