Several tissue-staining methods are indicated throughout the Atlas and described below. Shortened forms for some of the methods are included in parentheses. The staining method, along with the approximate magnification for each image, is provided after the description for each histological slide.

Hematoxylin and Eosin (H–­­E)

This standard method is often used. Hematoxylin is a base dye that gives a deep blue colour tothe acidic substances of cell and tissue components. For example, the deoxyribonucleic acid of the nuclear chromatin stains intensely. Similarly, the ribonucleic acid composing the ribosomes of cytoplasm produces various shades of blue, depending on the abundance of these particles. Hematoxylin also stains blue the acidic mucopolysaccharides present in the amorphous intercellular substance of the cartilage. The various substances that are stained by hematoxylin are said to be basophilic. Eosin is an acid dye that binds to acidophilic proteins and stains them in shades from pink to red (e.g., the mitochondria in cytoplasm, the collagen in connective tissue).

Masson’s Trichrome (Masson’s Trichrome)

This general multi-coloured staining method includes acid fuchsin, ponceau, hematoxylin, and fast green combined with various mordants, such as iron alum, picric acid and phosphomolybdic acid. See the details of this method in one of the textbooks listed in the Histology Textbooks section. This method stains connective-tissue components bright green and stains cytoplasm, keratin, and muscle fibers in various shades of red and orange.

Verhoeff's Hematoxylin (Verhoeff)

In this method, hematoxylin is modified by ferric chloride. The iron hematoxylin produced gives a deep blue-black colour to the elastic fibres of connective tissue. This dye may be combined with those used in the Masson’s trichrome method or with eosin.

Periodic Acid-Schiff and Hematoxylin (PAS-Hematoxylin)

Periodic acid is an oxidant of 1–2 glycol or amino-alcohol bonds of carbohydrates and yields aldehydic groups. These aldehydes then combine with the Schiff reagent (acid fuchsin), giving an intense purple-red colour to polysaccharides (e.g., glycogen) or to glycoproteins. Thereafter, the hematoxylin stains the nuclei blue.

Toluidine Blue (Toluidine blue)

This dye is frequently used in histology, especially on semi-thin sections of tissues fixed with glutaraldehyde and embedded in epoxy resins (epon). Toluidine blue is a basic dye that stains acidic substances bright blue. Certain acidic components (e.g., chondroitin sulphuric acid in cartilage and heparin in mast cells), stain purple instead of blue with toluidine blue. In such cases, the stained substances are said to be metachromatic (i.e., having a colour different from that of the dye in solution).

Tannic Acid-Phosphomolybdic Acid-Amido Black (TPA)

With this method, amido-black, after exposure to mordants (tannic acid and phosphomolybdic acids), stains green the filaments or microtubules of the cytoskeletal components of certain cells.

Silvernitrate (Silver)

Following certain fixations, silver nitrate may bind and stain black a variety of cytoplasmic or connective tissue components. For example, silver is used to stain the fine reticular fibres found in connective tissue. It is also used to stain the Golgi apparatus of ganglion cells in some neurons.

Osmium Tetroxide (Osmium)

This substance is used to fix and stain various cell and tissue components. It has been extensively used in the preparation of tissues for electron microscopy. It is also used in light microscopy to permeate fat droplets in fat cells, staining them black. Lipid substances, such as the myelin that coats certain nerve fibres, are well fixed and stained black with osmium.

Iron Hematoxylin-E (Iron hematoxylin-E)

This hematoxylin treated with ferric chloride gives an intensely black or blue-black colour to various basophilic elements (e.g., elastic fibres, nuclei). It is usually followed by staining with eosin.

Wright-Giemsa (Wright-Giemsa)

This staining method is usually used on blood or bone-marrow smears in hematology laboratories. It is a combination of eosin wiht a derivative of methylene blue.

Crezyl Blue (Crezyl blue)

This dye is used on blood smears to identify reticulocytes.

Hematoxylin and Silver (Hematoxylin and silver)

Silver, which stains reticular fibrers black, may be supplemented with hematoxylin, which stains the nuclei of various cells deep blue.

Toluidine Blue and Eosin (Toluidine blue, eosin)

Toluidine blue, a basic dye, is occasionally used as an alternative to hematoxylin and is then followed by staining with eosin or other acidic dyes (e.g., acid fuchsin).

Toluidine Blue and Acid Fuchsin (Toluidine Blue - Acid Fuchsin)

This method is the same as Toluidine blue and eosin except that acid fuchsin is used instead of eosin as an orange-pink counterstain.

Aniline Blue and Orcein (Aniline Blue-Orcein)

Aniline blue and orcein is a method to show elastic fibres.

PAS-TPA (PAS-TPA)

Periodic acid-Schiff and amido black follow treatment with mordants (see PAS-Hematoxylin and TPA above).

None (None)

Not stained

Hematoxylin (Hematoxylin)

Hematoxylin

Iron Hematoxylin (Iron Hematoxylin)

SILVER, TOLUIDINE BLUE (Silver, toluidine blue)

Wright-Giemsa (7.5A); Crezyl blue (7.5B) (Wright-Giemsa (7.5A); Crezyl blue (7.5B))