About 13.8 billion years ago, there was a tiny singularity that contained all matter and spacetime. This singularity was incredibly hot and dense.
At one point, the singularity starts expanding outwards at an extremely rapid rate, coming to be known as the "Big Bang". A possible theory is that the distinction of the Strong Force from the Grand Unified Force triggered this expansion.
From 10-38 seconds to 10-4 seconds, the electromagnetic and weak fields become two different fields, and elementary particles like quarks and gluons are created along with antimatter.
From 10-4 seconds to 3 minutes, basic particles such as protons, neutrons, electrons, and neutrinos are created.
500,000 years later, Hydrogen and Helium atoms have formed. Photons are released, creating cosmic background radiation. The evidence of this radiation is still in the universe today as microwaves.
During the Era of the Atom, atoms form stars. Clusters of stars form the first galaxies. Redshifting, or the color of a galaxy as it moves away from ours, is used as support for the Big Bang Theory.