Due to their transparency, tissue samples' cellular and intracellular structures cannot be microscopically examined until dyes color them. Dyes are combined with other dyes and/or chemicals to make up stains. "Biological stains" refer to dyes/dye complexes used to stain tissue samples for microscopic analysis in the histology laboratory.
Biological stains exist as:
- General tissue stains - These use one to three dyes, such as hematoxylin and eosin (H&E), to differentiate the nucleus from the cytoplasm of cells.
- Special stains - These involve multiple dyes in combination physically or sequentially by staining procedure to demonstrate specific structures within cells and tissue sections, such as connective tissue elements, often not demonstrated by the H&E.
