system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Is it possible for an area to be fully saturated with photons?

Under the right circumstances could an area (volume of air/water/vaccum) become fully saturated with light photons, to the extent where no more could physically exist in that area?   Has this/does this ever occur in either nature or a lab?  What would the effects be (would it have weight etc.)?

Thanks in advance!
gpt
There's no fundamental limit with photons the way there is with electrons (e.g. electron degeneracy pressure)--however, photons have energy, so the energy contained within your space would keep increasing so long as you keep stuffing them into it. Assuming this concentration of energy doesn't destroy whatever reflectors you're using to keep the photons in place, eventually the energy density would get so high that it would collapse into a black hole.