A cool gallery of colliding galaxies featuring some pretty amazing shots though it is very hard to comprehend the scale.
Known as interacting galaxies, these are ones whose gravitational fields are affecting one another. So one might pull on the arms of another or in more extreme cases the two can collide.
Our own Milky Way looks set to collide with the Andromeda galaxy in about 4 billion years.
Photos are courtesy NASA and ESA.