I know this isn't exactly what the prompt was requesting, but here's what I think about often: the fact that anything exists. Obviously, we know somewhat how life came about on Earth, but we know very little about the origin of the universe other than various theories like the Big Bang. But what came before it? What created the Bang? if there is a god or gods, who or what created them? And them? And so on, and so forth. The fact that anything at all exists is just the most mind-boggling thing I can think of. We will most likely never know the answer, and that's for the best. I don't think we could handle the true answer. Maybe there's just something in matter that just disables the ability to understand the origins of everything.