Aerosols in the atmosphere react to incident sunlight. This light is amplified in the interior of the aerosol droplets and particles, accelerating reactions. Together with colleagues at ETH Zürich, Peter Alpert and Markus Ammann have directly imaged photochemically active particles with X-ray spectromicroscopy and quantitatively mapped where incident light was amplified by the shape of the particles. This lensing effect causes photochemical reactions to be two to three times faster on average and so it is recommended to be included in future climate models.