The element known for being the most abundant in the universe is hydrogen. It accounts for about 75% of the normal matter in the universe and is the key building block for stars and galaxies. Hydrogen's simple atomic structure, consisting of just one proton and one electron, makes it fundamental in various nuclear fusion processes in stars, including our sun. This element plays a critical role in the formation of heavier elements within stars and is integral to the chemical processes that led to the development of the universe as we know it today.