Stars primarily consist of hydrogen, the most abundant element in the universe, formed from the cooled energy of the Big Bang. Through nuclear fusion, stars convert hydrogen into helium and subsequently into heavier elements like carbon. As a star exhausts its fuel, it undergoes gravitational collapse, potentially resulting in a nova or supernova, which creates even heavier elements. The specific processes and outcomes depend on the star's mass and composition. Understanding these processes provides insight into the elemental makeup of stars and the universe.