i've seen a documentary about black holes, its very interesting..
the center of our milky way is a black hole, & the center of the andromeda galaxy is a black hole too (most spiral galaxies have black hole centers btw) ,milky way & andromeda are moving toward each other so when they collide (after a billion years or something) it will produce massive chaos (in terms of gravity) & these black holes actually 'eat one another' , & so a new & bigger black hole is produced along w/ a new galaxy..