Nature Reviews Chemistry, Published online: 03 June 2026; doi:10.1038/s41570-026-00836-5Oxidative stress arises from reactive oxygen species that are essential for signalling yet harmful when uncontrolled. Fluorescence imaging enables real-time, sensitive, organelle-level reactive oxygen species detection, and this Review outlines design principles for developing reliable probes to advance biological and medical research. MAO, monoamine oxidase; MPO, myeloperoxidase; NO, nitric oxide; NOS, nitric oxide synthase; SOD, superoxide dismutase.
