Used in microbiology and clinical diagnostics to identify acid-fast bacteria, particularly Mycobacterium species such as Mycobacterium tuberculosis and Mycobacterium leprae. The stain helps differentiate these organisms from other bacteria due to their high mycolic acid content in the cell wall, which resists decolorization by acid-alcohol. After staining, acid-fast bacteria appear bright red against a blue or green counterstained background, allowing for easy visualization under a light microscope. Commonly used in sputum analysis for tuberculosis diagnosis in resource-limited settings due to its simplicity, low cost, and reliability. Also applied in histopathology to detect mycobacteria in tissue samples.