The Andromeda-Milky Way Collision
Currently, our planet Earth is happily residing in the Milky Way. We say currently because The Andromeda galaxy is heading straight for us. When the two galaxies collide, the crash will cause both of them and their supermassive black holes to merge creating a super, supermassive black hole. The good news is none of us will be around to see it. The event won't take place for at least another four billion years.