During the staining process of tissues, hematoxylin and eosin are commonly used chemical reagents. Hematoxylin is a basic dye that stains the nuclei a blue/purple color. It also stains RNA in ribosomes and rough endoplasmic reticulum. Eosin is a counterstain used after hematoxylin, and stains the cell’s cytoplasmic organelles a pink/red color.