There are three broad categories of biological stains:
- General or Routine Stains: Used to differentiate between the nucleus and the cytoplasm. This allows for the different tissue types to be distinguished from one another. These stains use one, two, or sometimes three dyes. The H&E stain falls into this category.
- Special Stains: These are used to demonstrate specific elements within the tissue, such as connective tissue, muscle, carbohydrates, lipids, pigments, and nerve tissue.
- Heavy Metal Impregnation: Involves the deposit of metallic substances onto targeted cells. This is often used to demonstrate nerve cells and certain microorganisms.