The wikipedia article on Bose-Einstein condensates mentions that helium-4 is, or can be, a boson. It says that a condensate is made by putting many bosons, such as helium-4, into the lowest energy state. How can an atom be a boson? I figured that an atom, composed of fermions, would have to be a fermion as well. How do the electrons and protons of helium-4 occupy the same space?