Where did the calcium in your bones and iron in your blood come from? From stars! Stars are like factories that turn hydrogen atoms formed in the Big Bang into heavier elements, including most of the stuff that you’re made of.

Here’s how it works: Nuclear reactions inside stars fuse hydrogen atoms to make helium, helium to make carbon, and so on through elements as heavy as iron. Anything heavier than iron is created when high mass stars blow up in enormous explosions called supernovae. These violent events seed space with all the elements, which then serve as building blocks for a new generation of stars—and eventually planets and people.