Until around a few hundred million years or so after the Big Bang, the universe was a very dark place.
There were no stars, and there were no galaxies.
After the Big Bang, the universe was like a hot soup of particles (i.e. protons, neutrons, and electrons)..
The Early Years
Until roughly 380,000 years after the Big Bang, the entire universe was a thick opaque cloud of plasma of electrons and nuclei.
As the universe expanded, it cooled off enough to let the plasma become atoms, and the cosmos became transparent..
Research published in 2015 estimates the earliest stages of the universe's existence as taking place 13.8 billion years ago, with an uncertainty of around 21 million years at the 68% confidence level. Diagram of evolution of the (observable part) of the universe from the Big Bang (left), the CMB -reference afterglow, to the present .
The timeline of the early universe outlines the formation and subsequent evolution of the Universe from the Big Bang (13.799 ± 0.021 billion years ago) to the present day.
An epoch is a moment in time from which nature or situations change to such a degree that it marks the beginning of a new era or age .
