1. DAPI is frequently used for staining nuclei.

2. Wash and harvest cells.

3. Fix cells. For example, mammalian cells can be fixed in 4% PBS buffered paraformaldehyde. Yeast cells may be fixed in 70% ethanol (and sonicate for 5 seconds).

4. Wash cells with PBS.

5. Stain cells in 0.1-1 mg/ml of DAPI in PBS for 20 minutes to 2 hours.

6. Wash cells with PBS.

7. Mount, seal with nail polish and keep in dark before viewing under a fluorescence microscope.