According to the Wikipedia article on atomic nucleus, captioned on an impression of helium atom, it states that
This depiction shows the particles as separate, whereas in an actual helium atom, the protons are superimposed in space and most likely found at the very center of the nucleus, and the same is true of the two neutrons. Thus, all four particles are most likely found in exactly the same space, at the central point.
How is this possible? Does this not violate Pauli's exclusion principle?