Fluorescent DNA-binding dyes are among the most important tools for scientists who use microscopy to study cell cycles or DNA’s dynamics in the nucleus. But existing dyes have limits. They don’t work in living cells, or they must be excited with ultraviolet light, which in extended doses can damage or kill cells. Two other options are now available, courtesy of Fredrik Westerlund of Chalmers University of Technology in Sweden, James N. Wilson of the University of Miami, and coworkers. They’ve developed a pair of stains that work at lower-energy wavelengths, which happen to match the laser wavelengths used in most fluorescence microscopes (Org. Lett., DOI: 10.1021/ol400268t). The molecules feature a π-electronic system that enables excitation at visible wavelengths, rotatable arms that control fluorescence emission, and cationic units that can interact with DNA’s phosphate backbone. Although similar in structure, each dye binds DNA differently. In kidney and breast cancer cells, the dyes are brighter than established dyes. That means researchers can use less dye and lower illumination intensities in cellular studies. These capabilities might be useful for prolonged imaging experiments in live cells or tissues, the team says.