Visualization of the electron number density in the core region of 16 clusters of TNG-Cluster at z = 0. Each panel shows the central 20% of r_500c projected along a line of sight of 15 kpc. The halo mass M_500c of each cluster is indicated in the panels. In the upper right of each panel, we also label the core state of each cluster based on the central cooling time. The aperture of 0.012 r_500c used to compute the central cooling time is depicted by black circles in the maps (see text). The clusters were chosen to reflect the diversity of the simulated cluster masses and to show the wide range of different morphologies of the gas.