The primary chemical component of stars is hydrogen. In the early universe, hydrogen formed shortly after the Big Bang and remains the most abundant element in stars today. Through the process of nuclear fusion, hydrogen atoms combine under immense pressure and temperature to form helium and release vast amounts of energy, creating light and heat. This energy is what causes stars to shine and is crucial for the formation of elements during stellar evolution. Understanding the composition and processes of stars helps scientists comprehend the universe's formation and the life cycles of celestial bodies.