To our knowledge, the brain is the most complex organized matter in the universe. We know of nothing as complex in anyone's experience. How does three pounds of very complicated stuff allow us to experience a world?
If you think about it carefully, the entire scope of the universe, all of that volume that you're conceiving of now, is actually occurring inside your skull. So everything in your world, your entire universe, resides in the confines of your skull, including your concept of your own brain.