The Ziehl-Neelsen stain is a special staining technique used primarily to identify Mycobacterium species, including the bacteria that cause tuberculosis. This method highlights the presence of mycolic acids in the cell walls of these bacteria, making them appear bright red under a microscope, while other cells take on a blue color. This staining process involves several steps, including the application of a primary stain, carbol fuchsin, followed by heating to facilitate dye penetration. After decolorization with acid-alcohol, a counterstain, typically methylene blue, is applied. The Ziehl-Neelsen stain is crucial in clinical microbiology for diagnosing infections caused by acid-fast bacilli.