A thought experiment: Let's say you have a piece of sand, and you have it to break it down. You break it down into silicon atoms. You further break it down into electrons, protons and neutrons. You can further breakdown protons and neutrons into quarks. As per the current state of physics, this is as far as you can go. Quarks and electrons are considered as fundamental particles.
Think about it. How is it possible that you cannot break something down further. What is a quark made up of.
Hypothetically, let's say you can actually break down a quark into X and Y(something that we haven't discovered yet), but then what is X and Y made up of. We can keep repeating this exercise as we breakdown smaller and smaller particles.
From this, It seems to me that matter doesn't actually exist. It's merely an illusion that results from something more fundamental.
I don't know yet, what that underlying fundamental entity is.
Even if we find that deeper abstraction, the question would still remain. What is that entity in turn is made up of.
The more I think I know, the more I realise the magnitude of how much I don't know, and things that I perhaps will never know.
Recommended watching