A fundamental laboratory technique that is introduced in general biology and microbiology courses is staining of bacterial cells on glass slides for visualization and characterization purposes. A common procedure, the Gram stain, differentiates between bacterial species based on the chemical composition of their cell walls. The staining procedure involves applying a primary stain, crystal violet, followed by Gram’s iodine, which acts as a mordant, decolorizing with an organic solvent such as ethanol, and counterstaining with safranin. Following the procedure, gram-positive bacteria, which are more resistant to decolorization, appear purple in color while gram-negative bacteria, which are more sensitive to decolorization, appear pink.