X-ray photon correlation spectroscopy
X-ray photon correlation spectroscopy (XPCS) in physics and chemistry, is a novel technique that exploits a coherent X-ray synchrotron beam to measure the dynamics of a sample. By recording how a coherent speckle pattern fluctuates in time, one can measure a time correlation function, and thus measure the timescale processes of interest (diffusion, relaxation, reorganization, etc.).
Source: Wikipedia — X-ray photon correlation spectroscopy (CC BY-SA 4.0)