The most abundant element in the universe is hydrogen. Comprising about 74% of the universe's elemental mass, hydrogen is the simplest and lightest element, consisting of just one proton and one electron. It plays a crucial role in the formation of stars and galaxies, as it is primarily found in stellar hydrogen gas clouds. In stars, hydrogen undergoes nuclear fusion processes, converting it into helium and releasing energy that powers the stars. Hydrogen's abundance is foundational to the universe's structure and dynamics, influencing cosmic evolution and the chemical makeup of celestial bodies.