No, we don't know everything yet, but we're continually getting closer. Take the core of Andromeda for example.
The Andromeda galaxy (aka M31) is our closest neighboring galaxy, and we think it's a lot like ours (the Milky Way). Eleven years ago we didn't know why the center was black, then the Hubble discovered it's a supermassive black hole. The next mystery was what's the blue glow around the center. Now Hubble's revealed that it's a disk of young blue giant stars. The disk is 1 light-year across and contains some 400 stars. Around that is a larger disk of old red stars about five light-years across (not sure how many of them).
To put things in perspective, the next star over from ours, Proxima Centauri (part of the Alpha Centauri system) is 4 ly away. And in the center of Andromeda there's 100 times that many stars in a diameter one fourth of that. We suspect the same thing is going on in the center of our own galaxy, as we've seen a number of bright blue stars there. Also if it were an uncommon thing, what's the chance that the only galaxy doing it would be the one next door? (That sort of ex post facto argument has flaws though, similar to the anthropic principle.)
Why is this freakish stuff going on in the core of a galaxy? We've no clue. But I bet we will in another 10 years. Maybe an IDer would say "God did it" and stop there, but not astronomers.