Two examples of Bose-Einstein condensates include superfluids, such as cold liquid helium, or superconductors, such as the nucleons inside a neutron star. Bose-Einstein condensates are another state of matter, similar to solids but with less energy. They were not directly observed until the 1990s, even though Einstein predicted their existence in the 1920s.
Bose-Einstein condensates exhibit peculiar characteristics and form in only the most extreme circumstances. In the case of a neutron star, the atoms are crammed so closely together that they behave as though they were a single atom. Neutron stars are among the densest objects known in the universe. If a baseball were made of the material from a neutron star, it would weigh more than 20 trillion kilograms. In fact, the escape velocity required to launch a rocket from the surface of a neutron star is about half of the speed of light.
Cold liquid helium becomes a superfluid. This means that the substance has no viscosity, or resistance to flow. A glass container full of supercooled helium cannot contain the substance. This is because the individual helium atoms can squeeze between the atoms of glass. Additionally, when kept in a container, such superfluids will crawl up the sides of the vessel and spill over the edge.