Giorgio Torrieri

At the Large Hadron Collider, not only nuclei but also individual protons collide. Even in such small systems, collective behavior resembling the flow of a liquid is observed. But the proton is a quantum object; its state is described by a wave function, not by temperature and pressure.

Back in the 1930s, Fritz Zwicky noticed that the speeds of galaxies in clusters were too high for the visible mass. Later, Vera Rubin confirmed this for individual galaxies.