Why is hematoxylin used to counterstain tissues or cells after IHC and ICC, respectively? It seems that hematoxylin only stains a few select things, like iron and chromatin.

Hematoxylin is the most widely used nuclear stain and is the H in an H&E, hematoxylin and eosin. An H&E should be the first routine stain done on all tissues.

Hematoxylin is used in immunohistochemistry as a counterstain to stain the nuclei of the cells.

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