Our most precise timepieces are atomic clocks, which exploit precise atomic transitions in the microwave and optical bands. Better clocks could come from nuclear transitions, which suffer less from external perturbations, but the only feasible known nuclear state is 229mTh. Now, Lars von der Wense of Ludwig-Maximilians-Universität Munich and colleagues have detected this state directly by searching for α decays in 233U. The half-life was measured to be longer than 60 s and the isomeric energy constrained to be between 6.3 and 18.3 eV, raising hopes that nuclear clocks could become reality.