Generally, matter exists in three distinct forms: as a solid, a liquid or a gas. Past physics research, however, has unveiled other curious states of matter, one of which is supersolidity. In a supersolid state, particles are arranged into a rigid crystal and can nonetheless flow through the solid without any friction. Although this may appear contradictory, this state is allowed by the laws of quantum mechanics.
Source:
https://phys.org/news/2019-07-unveils-supersolid-phase-dipolar-bose-einstein.html