Reading about teeth on this website, I came across this link and picture of a human child skull, where we can see how both sets of teeth are placed.
It made me wonder: after the second set of teeth move into the mouth (do they actually move?), what happens to the space they occupied before, while they were hidden?
Or do they not actually move, but stay in place and the mouth/skull/bone grows in size to expose them? I'm not sure which way it is.