A black hole. Scientists have spent years analyzing them. Trying to understand how they are born. Why are they there. Do they even exist? In recent years. Black Holes have been spotted at the centre of galaxies. The give-away sign, is a massive burst of energy, coming from the centre of some galaxies. These bursts of energy are called 'quasars'. The result of a black hole discharging vasts amount of energy it couldn't handle.
It is speculated that the human brain has 100 trillion different connections. It has also been speculated that the human brain is directly connected to the Universe. Read more in this Article.
Mankind has launched rockets into space. Discovered atoms. Discovered other planets, not just in our solar system, but in our galaxy and other galaxies. We can create technology. We can observe the Universe. But we can not understand our own brain.