[Sephiroth]

The "Big Bang" is highly controversial, imo. The expansion has an empirical basis of observation of the red-shift of light from receding galaxies. There is some evidence that the expansion is taking place at an accelerating rate, which is not consistent with big-bang.

The scientists are beginning to bottom out what the elementary particles do and how they combine in chaos to create matter as we know it. We are made of that matter and our molecules and bodies all hang together notwithstanding the atomic forces going on in said atoms/molecules.

Eventually, I expect all that research to reach a hard stop when everything about matter, elementary particles is known - in the frame of the tangible universe.

The rest will be speculation - like how were the elementary particles created? Have they always existed and were never created? After all, without these elementary particles, we couldn't be having this discussion.