The most abundant gas in the universe is hydrogen. Comprising about 75% of the elemental mass of the universe, hydrogen plays a crucial role in the formation of stars and galaxies. It exists primarily in a molecular form (H2) in space, where it is found in large clouds of gas and dust. Hydrogen is the first element on the periodic table and the simplest, with only one proton and one electron. Its abundance contributes to nuclear fusion processes in stars, powering them and resulting in the creation of heavier elements, which are essential for the formation of planets and life.