The modern human mind has developed to the point that it can comprehend the immensity of two galaxies colliding, in all its detail, and simulate the event.
The accompanying image is an example from a computer simulation showing how two young galaxies, among the earliest galaxies formed in the universe, may have collided with one another. Through such mutual cosmic “cannibalism,” most of today's large galaxies—including the galaxy in which we live—formed billions of years ago.
American astronomer Phil Plait explains more about this process in the original link below, although he himself admits that words can hardly describe the phenomenon. A second original link provides details about the image. [source] [source]