I once read a sci-fi book about vehicle that allowed the crew and it to get smaller and smaller. Nothing very special right? We've seen Antman. But when the tra

I once read a sci-fi book about vehicle that allowed the crew and it to get smaller and smaller. Nothing very special right? We've seen Antman. But when the travelers got really nucleus small they saw they were approaching a ball, and it turned out that ball was a universe and as they entered it they could then start exploring its things and as they get further smaller they got into the atom-size in that universe and then again saw a set of spheres and could go into them, and get smaller there and so on, without end. Within atoms there were universes within which there was more universes and so on ad infinitum. Does that make sense? I've forgotten the name of the book.