Liquid helium climbs out of its cup

Below 2.17 kelvin, helium-4 becomes a superfluid and creeps as a thin film up and over the walls of an open container.

At the lambda point, 2.17 K, helium-4 undergoes a transition. A fraction of the atoms occupies a single quantum state. That fraction flows without friction. A film a few dozen atoms thick crawls up glass, over the rim, and down the outside until the levels match or the cup is empty.

It will also leak through gaps that would stop any ordinary liquid, and a fountain will start itself if you heat the powder it is standing in. These are not metaphors. They are demonstration experiments, filmed, in every low-temperature lab that can afford the dewar.