Chromosomes are deep compression of genetic material with hereditary properties within the cell to form aggregates, easily stained by alkaline dyes into dark colors, so called chromosomes (chromatin), chromosomes and chromatin is the same material in the interphase of cell division and the division of the different morphology of the manifestation of the different phases only. Chromosomes appear in anaphase, chromatin appears in interphase, filamentous, its essence are deoxyribonucleic acid (DNA) and protein combinations (i.e., composed of nucleoproteins), unevenly distributed in the nucleus of the cell, is the main carrier of genetic information (genes), but not the only carrier (such as mitochondria in the cytoplasm).

Many dyes have varying degrees of affinity for DNA and can therefore be used as stains for chromosomes. In the routine staining of chromosomes, good staining results can generally be obtained with giemsa, lichen red, forskolin, and carbolic acid compound red. Sulfur cordial staining solution (1%) can be used for chromosome staining of oral mucosa, urine, amniotic fluid, chorionic villus cells and artificially cultured cells and other samples, especially for the staining of sex chromatin which is difficult to color; sulfur cordial staining can also be used for the staining of mast cells, the heterochromatic material is purplish-red, and the other is blue.