The gas most commonly used in balloons is helium. Helium is a colorless, odorless, and non-flammable gas that is lighter than air, allowing helium-filled balloons to float effortlessly. Due to its inert nature, helium is considered a safe choice for filling balloons, unlike hydrogen, which is flammable. Helium is often extracted from natural gas deposits and is used in various applications beyond balloon inflation, such as in medical imaging, cryogenics, and even as a coolant for some superconducting magnets. Its unique properties make it a highly prized gas in both scientific and entertainment contexts.