Eosin can be used to stain cytoplasm, red blood cells, collagen, and muscle fibers for histological examination. It is most often used as a counterstain to hematoxylin in H&E staining
It is typically pink, with different shades of pink for different types of connective tissue fibers. Eosin Y is the most commonly used form of eosin and may be used in both water and alcohol.