Improving on organic photosensitizers: The photoexcitation of metal nanoparticles results in the formation of singlet oxygen and its phosphorescence emission (see picture). As the nanoparticles are resistant to both photoinduced and enzymatic degradation and also have impressively high extinction coefficients, these findings may have an impact on techniques for the generation of singlet oxygen in biological settings. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.