Superfluids have many extraordinary properties. They behave like typical constituents of solutions, with all the properties associated with normal fluids and superfluid constituents. For example, it is impossible to create a temperature gradient in a superfluid, just as it is impossible to create a potential difference in a superconductor.
Superfluidity was discovered in 1937 by Pëtr Leonidovič Kapica, John F. Allen and Don Misener. The study of superfluids is called quantum hydrodynamics.
An important application of superfluids is in dilution refrigerators. In chemistry, superfluid helium-4 has been successfully used as a quantum solvent in spectroscopic techniques. This technique, called Superfluid Helium Droplet Spectroscopy (SHeDS), is of great interest in the study of gas molecules, since a single molecule solvated in a superfluid medium benefits from freedom of rotation: the molecule behaves as it would in the gas phase.