Helium-4 is a stable isotope of helium, consisting of two protons and two neutrons in its nucleus. It is the most abundant isotope of helium, making up about 99.99986% of natural helium found on Earth. Helium-4 is a colorless, odorless gas that is lighter than air and is commonly used in balloons and as a cooling medium in cryogenics. This isotope is produced through the nuclear fusion processes in stars, including our Sun, and is also generated during the radioactive decay of certain elements. Helium-4 has unique properties, such as low boiling and melting points, which make it useful in various scientific and industrial applications, including liquid helium for superconducting magnets.