Howling:Human expansion into other galaxies

I'm trying to research the space age for humanity, comparing the Earth Empire's time to the rest of the galaxy, since it seems to be replaced by the Galactic Federation in the 30th century, and I know humans have spread to three galaxies by the 42nd century, but is there a definitive era or one that can be narrowed down to where humanity starts to explore/colonize another galaxy other than the Milky Way? Steed ☎  04:32, February 20, 2017 (UTC)