At temperatures near absolute zero, helium becomes a superfluid that flows without friction and can climb up walls.

Superfluidity was first discovered in 1937 by Pyotr Kapitsa, John F. Allen, and Don Misener. They observed that when helium-4 is cooled below the lambda point of 2.17 Kelvin, it undergoes a phase transition into a quantum state called Helium II. In this state, the liquid behaves according to quantum mechanics rather than classical physics.The absence of viscosity means that Helium II has no resistance to flow. This lack of friction allows the liquid to form a thin film, called a Rollin film, about 30 nanometers thick that crawls up the surfaces of its container. This phenomenon is driven by surface tension and capillary action, which are no longer hindered by internal fluid friction.Because the atoms in a superfluid occupy the same quantum state, they move as a single coherent entity. This allows the fluid to leak through cracks so small that even air cannot pass through them. If placed in a circular loop, a superfluid could theoretically circulate forever without slowing down.This discovery was so significant that Pyotr Kapitsa was awarded the Nobel Prize in Physics in 1978. Today, superfluids are essential for cooling the superconducting magnets in the Large Hadron Collider at CERN. They also provide a unique environment for studying the fundamental laws of quantum mechanics on a macroscopic scale.