Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Eosin is a red fluorescent dye used to stain cytoplasmic material, cell membranes, and extracellular structures in microscopic specimens. It is often applied in combination with hematoxylin to highlight different cellular components.
5 Must Know Facts For Your Next Test
Eosin is an acidic dye that binds to basic (alkaline) components of the cell.
In the Hematoxylin and Eosin (H&E) staining method, eosin stains cytoplasm, collagen, and muscle fibers pink or red.
Eosin can be used in both aqueous and alcoholic solutions for staining purposes.
It is commonly used in histology and pathology for examining tissue samples under a microscope.
Eosin Y and Eosin B are two different forms of eosin dye; Eosin Y is more commonly used.
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Related terms
Hematoxylin: A basic dye that stains acidic structures like nuclei blue or purple.
H&E Staining: A common staining technique using hematoxylin and eosin to differentiate between cellular components.
Histology: The study of microscopic structures of tissues.