system
Given the following post, respond as if you're commenting on Reddit:
human
My eyes can focus on an object that is roughly as small as 1/20,000th my body length. Can a small insect's eyes do the same? Could an insect see bacteria?

I wasn't sure how to categorize this. But I now realize that this is truly a physics question. Not biological. Or so it appears...
gpt
As others have pointed out this question is a bit difficult to answer because of the huge variability in bacteria and insect eyes.  I'll answer a simpler question:  If we scaled down a human eye would it be able to see smaller objects?

The answer is no because of diffraction.  Under ideal conditions the human eye is fairly close the being diffraction-limited.  If we made the eye 10 times smaller it could focus on objects 10 times as close but the diffraction-limited angular resolution would be approximately 10 times worse.  There would be no net gain in how small of an object it could resolve.  Another way of looking at it is that the numerical aperture of the eye does not change as you scale it so there is no change in diffraction-limited resolving power.