What's the smallest thing in the universe?

Trick question.

The 'smallest thing in the universe' is an undefinable, imaginary concept. Most sources quote that quarks are the smallest known objects in the universe, and others postulate theories in which smaller objects may exist.

Beyond this, lies the magical zone between the mortal barrier of perceptibility, and the next generation of universe in all its original vastness. Our lives mimic the life cycle of the universe because we are entwined with it.

In a perverse way, it makes sense. And yet, you can never devise any sort of test to prove it. It is a religion all to itself.

Or, does a deity reside within this magical, unseen, postulated area of reality? Some sort of resemblance to an actual earthly religion's description? I don't know.

TLDR:

You can see things smaller and smaller until something in a place you can't see becomes as large as the whole universe. I don't know.