What exactly does the U.S. capitol hold?

I know that there are senate and house chambers, but what about all the areas between that and the rotunda? I know that congressmen have offices outside the building, but do any congressmen have offices inside the building? I can't for the life of me find a floor plan online, and am so curious as the whether or not there are congressional offices inside the U.S. capitol, and if not, what is in there?