27% of the material world is made up of dark matter. The existence of dark matter is accepted by most astronomers today but they have no idea of what this strange stuff actually is. That's why they use the word dark. They could have said mysterious matter, weird matter or unknown matter, but they prefer the word dark. They understand that it must be there when they observe the expansion of the universe but they don't understand what it is.
Ordinary matter and ordinary energy, the stuff that physicists can detect with their powerful high tech instruments, constitute less than 5% of the universe.
The being that you believe is you and your consciousness, is only the tip of an iceberg. The main part of you is hidden. Freud called that part the unconscious.
You do not know who you are. You do not know what life is all about, really. The main part of you is a mystery. The main part of the world is a mystery.
The world we live in, the world we can see and touch, hear and smell, is just a tiny fraction of it all.
When you think that you understand what life is all about and when you think that you are realistic, then you are deluded.