Cooled just below 2 Kelvin, liquid helium flows with zero friction at all

In 1937, Pyotr Kapitsa cooled helium below 2.17 Kelvin and found it lost all viscosity, flowing through gaps too narrow for ordinary liquids and even creeping up and over the walls of its own container. He named the phenomenon superfluidity; physicists John F. Allen and Don Misener independently reported the same effect the same month. Kapitsa didn't receive the Nobel Prize for the discovery until 1978, four decades later.

— Pyotr Kapitsa, Viscosity of Liquid Helium below the λ-Point — Nature, 1938