Before The Big Bang there was nothing at all. No galaxies, no stars, no planets and no life. No time, no space, no light and even no sound! Then suddenly it all began!
The cosmos goes through a super inflation, expanding from the size of an atom to that of a grapefruit in a tiny fraction of a second.
Post-inflation, the universe is a seething, hot sup of electrons, quarks and otherparticles.
A rapidly cooling cosmos permits quarks to clump into protons and neutrons.
Still too hot to form into atoms, charged electrons and protons prevent light from shining: the universe is a superhot fog.
Electrons combine with protons and neutrons to form atoms, mostly hydrogen and hellium. Light can finally shine.
Gravity makes hydrogen and hellium gas coalesce to form the giant clouds that will become galaxies; smoller clumps of gas collapse to form the first stars.
As galaxies cluster together under gravity, the first stars die and spew havy elements into space. Those will eventually turn into new stars and planets.