Hoechst 33342 nucleic acid stain is a popular cell-permeant nuclear counterstain that emits blue fluorescence when bound to double-strand DNA. This dye is commonly used to distinguish condensed pycnotic nuclei in apoptotic cells and for cell-cycle studies in combination with BrdU.

Excitation Wavelength: 358nm (ultraviolet light)

Emission Wavelength: 461nm (blue/cyan fluorescence light)