The first experimental demonstration of the control of certain instabilities in a tokamak plasma using circulating energetic ions is reported this week in Nature Communications. The work was carried out at the Joint European Torus — the largest global magnetic confinement plasma physics experiment — and marks an important step for tests in reactor relevant plasmas. Tokamak plasmas form the basis of many current plasma fusion experiments but they suffer from magnetic instabilities. Schemes to control these instabilities are often power-hungry and reduce the reactor efficiency. Building on earlier theoretical and experimental demonstrations, Jonathan Graves and colleagues successfully injected energetic ions into a high confinement mode plasma during a pulse of the Joint European Torus, which lead to control of the sawtooth instabilities and reduced disruption of the plasma. This demonstration paves the way to effective control of magnetic instabilities without compromising performance in future plasma reactors.