Everything, including us, is essentially made from star dust. Hydrogen and helium were produced in the Big Bang. But most other elements were produced by nuclear reactions in the interiors of stars over successive generations. When a star dies, or explodes as a spectacular supernova, a fraction of its synthesized elements is released into the interstellar gas clouds. The clouds eventually coalesce to form successive generations of stars, which produce more and more elements. Thus the oldest stars have the fewest elements, while the newer ones have more. Image couretsy NASA