A protein crystal consists of a regularly ordered array of protein molecules. The molecular structure is determined from the pattern of X-ray light (called a diffraction pattern) that is scattered from this periodic array. Unider illumination from an ultra-intense X-ray pulse from a free-electron laser the crystal explodes. This initiates as an atomic disordering of all the constituent molecules. As this disorder increases in time (which flows down the picture) the crystal loses definition initially at the highest resolution, and later at lower resolution, causing a corresponding termination of the detected diffraction. Even if pulses are much longer than the explosion timescale, the measurement corresponds to the undamaged molecule.