When the star ten times more massive than our own Sun, explodes (Supernova) it leaves behind the strangest phenomenon in the Universe. The Black Hole. After explosion what is left behind is heavy core of subatomic particles, a Neutron Star. It can be very small, but with enormous density. Scientists calculated that approximately one teaspoon of Neutron Star would weight around billions of tons. The gravitational pressure of this highly dense object is so large that it can bend fabric of time and space. This theory is based on Einstein's proposition that space and time are woven together in a flexible fabric. Massive objects like Sun warp the fabric of space and time and pull smaller objects like Earth. Very large Neutron Star can warp time and space fabric so much that it could create a hole where gravity is so strong that not even light could escape. Black Holes are pulling everything around them closer to the center of the hole. In some sense black holes are creators of the galaxies since they are pulling planets and stars towards the spiral center. Each galaxy has a Black Hole and occasionally galaxies collide together because of the gravitational pull from the larger black holes. It is expected that in 5 billion years Andromeda galaxy will collide with our Milky Way galaxy.