Carbol fuchsin is a synthetic dye commonly used in microbiology for staining bacteria. It is a red dye that helps visualize certain types of cells under a microscope, particularly in the Ziehl-Neelsen stain for identifying Mycobacterium tuberculosis, the bacterium responsible for tuberculosis. This dye works by penetrating the cell walls of bacteria, allowing them to be seen more clearly. Carbol fuchsin is often used in combination with heat to enhance its staining ability, making it an essential tool in laboratory settings for diagnosing infections and studying microbial structures.