| The hot gas in the intracluster medium (ICM) is perturbed by smooth mass accretion, mergers, feedback from active galactic nuclei (AGN), motions of galaxies, and other processes. These processes could drive turbulence, which plays an important role in energy transfer, ICM heating, and star formation. Direct turbulence measurements through Doppler line broadening and resonant scattering of X-ray photons require high-resolution X-ray spectra. I will discuss what we have learned so far from the high-resolution XMM-Newton/RGS observations of compact cores of galaxies and groups and the near-future XRISM observatory, focusing on turbulence-related science planned for the Performance Verification phase. |