A collaboration of scientists from five of the world’s most advanced x-ray sources in Europe, Japan and the US, has succeeded in verifying a basic prediction of the quantum-mechanical behavior of resonant systems. In the study published in Nature Physics, they were able to carefully follow, one x-ray at a time, the decay of nuclei in a perfect crystal after excitation with a flash of x-rays from the world’s strongest pulsed source, the SACLA x-ray free electron laser in Harima, Japan. They observed a dramatic reduction of the time taken to emit the first x-ray as the number of x-rays increased. This behavior is in good agreement with one limit of a superradiant system, as predicted by Robert H. Dicke in 1954.