Many scientists think that strings are the fundamental objects of reality, and they might be correct in their assumption. Why do they think this? Better yet what the hell is a string???
Well, there are many different reasons to think that nature’s smallest parts are tiny little filaments of energy. For one thing, we know from the work of Max Planck that there is a minimum for everything (i.e. smallest duration of time, shortest distance of space, etc…), so in many ways the tiniest object is just an extension of that logic.
Now, although strings would be far too small to detect if they actually do exist, scientists have observed that high energy collisions produce what appear to be the vibrations of some kind of plucked strands of energy at really small scales. This phenomena leads to the impression that there are little slivers of stuff that make up the fabric of reality.
In addition to this, a number of elegant mathematical models predict what the ontological status of our world is at the basement level. Brilliant minds like that of Edward Witten have produced descriptions of the world that could very well turn out to be correct.
The problem is that there is no way to prove that string theory is anything more than just a theory. Unlike evolution which can be experimentally verified in the lab, we may never be able to probe deep enough to ever know what’s really down there.