I was reading today about superfluids and the like. They were talking about how at a certain low temperature bosons will all go into their ground state. I'm trying to get a physical feel for what this means. If a mole of helium 4 atoms(boson) are cooled so that condensation occurs. What exactly happens? I can imagine, if there is no degeneracy pressure, then the mole of atoms can become extremely dense. But how dense can they get? Is the nucleus nucleus coulomb repulsion the only thing stopping them from becoming unified?