Spectroscopy Circular dichroism spectroscopy is widely used to distinguish between nonidentical mirror-image molecules. The technique relies on differential absorption of left versus right circularly polarized light and therefore tends to require solution-phase samples for adequate sensitivity. Daly et al. now report gas-phase circular dichroism spectra of DNA oligonucleotides based on detection of photodetached electrons rather than transmitted light (see the Perspective by Barran). The salient spectral features matched those in solution. Pairing the technique with mass spectrometry enables prior mass selection of particular molecules for analysis. Science , this issue p. [1465][1]; see also p. [1426][2] [1]: /lookup/doi/10.1126/science.abb1822 [2]: /lookup/doi/10.1126/science.abc1294