The hydrogen atoms in your body are nearly 13.8 billion years old—created in the Big Bang itself.

The Big Bang occurred approximately 13.8 billion years ago, creating the first subatomic particles. Within the first three minutes of the universe's existence, a process called Big Bang Nucleosynthesis began, producing the vast majority of the universe's hydrogen and helium. Because hydrogen atoms are stable and do not decay, the specific hydrogen nuclei in your water molecules today are the same ones formed at the dawn of time.While hydrogen is primordial, heavier elements like carbon, nitrogen, and oxygen were created much later through stellar nucleosynthesis in the cores of massive stars. When these stars reached the end of their lives, they exploded as supernovae, scattering these essential building blocks across space. These materials eventually coalesced to form our solar system and Earth roughly 4.5 billion years ago.Every atom in the human body has a long history of recycling through the biosphere. An atom of carbon in your DNA might have once been part of a Tyrannosaurus rex or a prehistoric fern. According to NASA and the Harvard-Smithsonian Center for Astrophysics, roughly 93 percent of the mass in the human body is composed of this ancient "stardust." This means your physical self is a collection of matter that has existed for nearly the entire history of the cosmos.