What stain barely colors the cytoplasm, but provides excellent nuclear and nucleolar detail. It is used when there are clumps of cells because their cytoplasm will not obscure their nuclei. It is also used when contamination of smears from red blood cells is present, because it does not stain these cells and therefore they will not obscure nucleated cells.

Cytology is the exam of a single cell type, as often found in fluid specimens. It's mainly used to diagnose or screen for cancer. It's also used to screen for fetal abnormalities, for pap smears, to diagnose infectious organisms, and in other screening and diagnostic areas."