Histological staining plays a critical role in the visualization of tissue and cell structures. Living cells or fixed cells have very few inherent colors and only very small differences in the refractive indices of their component parts. By staining tissue sections, pathologists and researchers can view tissue morphology (structure) or look for the presence or prevalence of particular cell types, structures or even micro-organisms under a microscope.
Histological staining includes routine staining and special staining. Routine staining refers primarily to the hematoxylin and eosin (H&E) stain, while special staining is used to refer to alternative staining techniques outside of routine H&E stain to provide specific information researchers or pathologists need.
Routine Staining
Routine (H&E) staining is the cornerstone of tissue-based diagnosis. It stains the nucleus and a few other substances in blue, followed by counterstaining with an aqueous or alcoholic solution of eosin which colors cytoplasm and eosinophilic structures into various shades of red, pink, and orange for initial microscopic evaluation of the tissues. If applied properly, this technique can provide exceptional details of tissue structure and cell composition. This detail is necessary for tissue-based diagnosis, especially in the detection and classification of cancer. H&E staining is the main method in histology, and is considered to be the “gold standard” for brightfield microscopy.