Which were the first elements to form after the Big Bang started to cool?

Scientists believe hydrogen and helium were the first elements to form out of the quark-gluon plasma that was produced in the Big Bang. 

All other elements in the universe are formed in nuclear fusion reactions that happen inside stars. Smaller elements like hydrogen and helium are fused together to form heavier atoms with more protons — atoms of different elements. 

All the atoms in the air we breathe, the clothes we wear, and the silicon in our computers was formed in a star that lived and died long ago.