Why does eosin colour cytoplasm?

Staining usually works by using a dye, that stains some of the cells components a bright colour, together with a counterstain that stains the rest of the cell a ... Another way of saying this is that cytoplasmic proteins are acidophilic (acid liking - i.e. bind to acidic dyes). ... H&E contains the two dyes haemotoxylin and eosin. read more

Eosin is an acidic compound; cytoplasm is basic (because most proteins and other structures in the cytoplasm are basic), so eosinophilic. read more

Eosin is most often used as a counterstain to hematoxylin in H&E (haematoxylin and eosin) staining. H&E staining is one of the most commonly used techniques in histology. Tissue stained with haematoxylin and eosin shows cytoplasm stained pink-orange and nuclei stained darkly, either blue or purple. read more

The structures do not have to be acidic or basic to be called basophilic and eosinophilic; the terminology is based on the affinity of cellular components for the dyes. Other colors, e.g. yellow and brown, can be present in the sample; they are caused by intrinsic pigments, e.g. melanin. Some structures do not stain well. read more