At the time of the big bang, the entire universe was.inside a bubble smaller than a pinhead; it was extremely hot and dense / the pinhead exploded and the universe we know was born; time, space and matter.
Within the first few seconds of the Big Bang, protons, neutrons and electrons were made.
The Big Bang theory evidence
Expansion of universe or galaxies (red shift)
presence of hydrogen and helium in gas clouds in distant galaxies