What is outside our galaxy?
A galaxy comprises star systems.
As a whole, these systems revolve around the galactic center, with periods in millions of light years (ly).
A galaxy extends for several thousands of ly across, with thousands of ly bulge, at the center..
Our Milky Way (MW) might comprise billions of star systems.
There might be hundreds of galaxies behind MW and hidden to us. Too many in our view around MW are detectable for enumeration and investigation.
Overall, this is currently the observable universe.