Increasing our understanding of cellular processes requires information about the types of biomolecules involved, their locations, and their interactions. This requires the molecules to be labeled without affecting physiological processes (bioorthogonality). This works when the markers are very quickly and selectively coupled using small molecules and 'click chemistry'. In the journal Angewandte Chemie, a team of researchers has now introduced a novel type of click reaction that is also suitable for living cells and organisms.