Acid-fast staining is a laboratory technique used to identify certain bacteria, particularly those in the Mycobacterium genus, such as Mycobacterium tuberculosis, the causative agent of tuberculosis. This method highlights the unique waxy cell wall of acid-fast bacteria, which retains the dye even after being washed with acid-alcohol. The process involves applying a primary stain, usually carbol fuchsin, followed by a decolorization step and a counterstain, often methylene blue. Acid-fast bacteria appear red under a microscope, while non-acid-fast bacteria take on the blue color, allowing for clear differentiation between the two types.