Staining allows visualization of tissue features. (a) an unstained image has little contrast while (b) the application of H&E stain highlights nucleic acid-rich regions as blue and protein-rich regions at pink. (c) structure of a prostate gland. It is notable that the stain is universal in that it is not diagnostic of cell type or disease. The stain serves only to provide contrast that is subsequently used by a human to recognize cell types and diagnose disease.
Kwak et al. BMC Cancer 2011 11:62 doi:10.1186/1471-2407-11-62