system
Given the following post, respond as if you're commenting on Reddit:
human
What created matter?

I would like to know what theories there are regarding how matter was created.
gpt
There are many layers to the question, and many open questions as well.

The matter we know was created after a period which we call reheating. During the first instants of the universe, it went into a very fast expansion called "inflationary period". Once this expansion ended, the energy that drove this expansion was converted into kinetic energy and mass of particles.

These very energetic particles were in some sort of very homogeneous plasma, and as the universe was cooling down progressively, this plasma started forming bound states - neutrons, protons.. and during at time which we call recombination, the electrons combined with neutrons and protons to form atoms.