Gegenfärbemittel
Gegenfärbemittel, also known as counterstains or secondary stains, are chemical substances used in microscopy to contrast with a primary stain, making structures more visible. They are typically applied after a primary stain has bound to specific cellular components, and they stain different components or the background. The principle is to use dyes with different chemical affinities and colors to highlight various parts of a specimen.
Common applications for gegenfärbemittel are found in differential staining techniques. For instance, in the Gram stain,
Another example is the Ziehl-Neelsen stain used for identifying acid-fast bacilli, such as *Mycobacterium tuberculosis*. Carbolfuchsin