the Ziehl-Neelsen stain is a laboratory technique used to identify acid-fast bacteria, particularly Mycobacterium tuberculosis, which causes tuberculosis. This staining method involves applying carbol fuchsin to the bacterial smear, decolorizing with acid-alcohol, and counterstaining with methylene blue. The acid-fast bacteria retain the red color, aiding in their identification under a microscope. This staining technique is essential for the diagnosis of tuberculosis and other mycobacterial infections in microbiology.