1.Hoechst33258,10mg/mlstockinDMSO. 2.Culturemedium. 3.15mlsterileconicaltube. 1.Ina15mlconicaltube,add1volumeHoechst33258stockto1000volumesofmedium.Need3mlforeachcoverlispdish.Mixthoroughly. 2.Removeallmediumfromtheculturedish,replacewiththedye-containingmedium. 3.Incubatefor30min. 4.Removedye-containingmedium.Rinsedishtwicewithregularmedium. 5.Addregularmediumtothedish.FluorescencecanbeobservedwithZeiss02UVfiltersetandquartz-halogenlamp.Mercuryarclampsyieldamuchhigherintensitybutcouldcausedamangetolivecells. Note:thesameprotocolcanbeusedwithethidiumbromide.ReplaceHoechststocksolutionwith10mg/mlaqueousstocksolutionofethidiumbromide.VitalStainingofChromosomeswithHoechst33258