Britannica Sources used in this answer

Why are chemical stains used when examining tissue samples?

Created from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles.

Tuberculosis — disease A doctor examining chest X-rays of patients infected with tuberculosis, which remains one of the world's deadliest diseases.

Chemical stains are essential in pathology and histology because they allow for the visualization and identification of specific structural and molecular components within tissue samples that would otherwise be difficult to distinguish.12

Through histochemistry, researchers use dyes that have a specific affinity for particular chemical constituents, such as glycogen, proteins, DNA, or RNA. By applying these stains, pathologists can determine the chemical properties of cell components, such as their acidity or alkalinity, and pinpoint the precise location of enzymes within a cell.12

Furthermore, staining techniques are critical for characterizing microorganisms. For example, the Gram stain exploits fundamental biochemical and structural differences in bacteria cell walls, allowing clinicians to differentiate between types based on how they retain or lose specific dyes. These methods transform transparent or uniform tissue samples into detailed, observable specimens, providing vital diagnostic information.31