Hydrogen is the lightest and most abundant element in the universe. Every hydrogen atom contains just one proton and one electron, making it simpler than any other element. Despite being the smallest element, hydrogen makes up about 75% of all normal matter in the universe.

Hydrogen gets its name from Greek words meaning “water former” because when hydrogen burns, it combines with oxygen to create water. This reaction releases tremendous energy, which is why hydrogen powers the sun and other stars. Deep inside stars, hydrogen atoms fuse together under extreme pressure and heat, creating helium and releasing the light and warmth that make life on Earth possible.

On Earth, pure hydrogen is a colorless, odorless gas that's much lighter than air. You rarely find hydrogen by itself in nature because it loves to bond with other elements. Water contains hydrogen bonded to oxygen. Natural gas contains hydrogen bonded to carbon. Even your own body is full of hydrogen: it's in the water you drink, the proteins in your muscles, and the DNA in your cells.

Scientists are working on using hydrogen as a clean fuel because when it reacts with oxygen, it produces only water vapor instead of pollution or greenhouse gases like carbon dioxide. Some cars already run on hydrogen fuel cells, and engineers dream of using hydrogen to power airplanes, ships, and even homes. For the hydrogen power to be truly “clean,” though, it needs to be produced with electricity from renewable sources.