As far as small things, that is also relative; to the naked eye, a human cell would be infinitesimally small (invisible), and on average an adult has 300 trillion of those. Bit hard but not impossible to wrap one’s mind around going smaller, to subatomic particles.
One of the things I learned from the David Butler series is that the majority — like 99% — of the mass of ordinary matter is not due to matter, it's due to the energy contained in the forces that hold the quarks together inside protons and neutrons, and the forces that hold the protons together within atomic nuclei. Quarks are held in proximity by the strong nuclear force, which is indeed very strong.
In the Butler lecture series, he said that to separate quarks from one another would require a force of 22 tons, not tons per square inch, but tons per quark.
If you could somehow exert this much force on them in such a way as to separate them, the energy you used to move them apart would be converted into matter, into a string of new quarks that would bridge the gap of separation between the two original quarks.
Isn't that strange and fascinating?
So that little bit of energy-mass is what has the spin! That's amazing to contemplate. Thanks for that insight. I'm afraid I glossed over it at first.
I listened to one video where the narrator said that the concept of quantum spin is the key to the nature of reality itself.
As an undergraduate in physics, my inability to grasp it, and the inability of my professors to explain it, is one of the things that drove me out of physics and into engineering.