Spotlight on copper Photoredox catalysis relies on visible-light excitation to accelerate a burgeoning number of chemical reactions. Initially, the technique relied primarily on complexes of precious metals, such as ruthenium or iridium, to absorb the light. Hossain et al. review recent progress in the use of copper complexes as an alternative. In addition to its Earth abundance, copper opens up a variety of distinct mechanisms involving electron transfer within the coordination sphere. Science , this issue p. eaav9713