Staining should be selective, and, ideally, should only stain the chromatin and not the cytoplasm. Chromatin is basophilic, whereas the proteins in the cytoplasm are acidophilic. Acidic solutions of basic stains, such as carmine, or amphoteric stains, such as orcein, permit the differential staining of chromatin. Several staining procedures are routinely used for studying plant chromosomes. Note: this list does not include in situ (ISH) and fluorescent in situ (FISH) hybridization procedures, which are covered in a separate section.