Gram staining is a laboratory technique used to classify bacteria into two groups: Gram-positive and Gram-negative. This method involves applying a series of dyes to a bacterial sample, which helps to visualize the cell wall structure. The first dye, crystal violet, stains all bacteria, while iodine acts as a mordant to fix the dye. After rinsing, a decolorizer, usually alcohol, is applied. Gram-positive bacteria retain the crystal violet stain due to their thick peptidoglycan layer, appearing purple, while Gram-negative bacteria lose the stain and are counterstained with safranin, appearing pink. This differentiation aids in identifying bacterial infections and determining appropriate treatments.