After staining, the cells may be quantitatively evaluated for DNA content visually or using commercially available imaging systems. This kit is designed for cytological specimens prepared from cytospins, smears, cell imprints, disaggregated tissue, or whole tissue. The basis of the Feulgen staining procedure uses the Feulgen reaction to specifically and quantitatively stain DNA in cellular material. Cells are treated with a mild solution of hydrochloric acid which splits the purine (adenine and guanine) and pyrimidine (thymine and cytosine) bases from the sugar-phosphate groupings and exposes the aldehyde groups. Aldehyde groups uncovered in the hydrolysis react with the Feulgen stain to form a stable, colored compound. The amount of stain color developed is directly proportional to the amount of DNA present in the stained nuclei.