  Recently predicted and observed Pauli crystals are structures formed by
trapped ultracold non-interacting particles obeying Fermi statistics. The
relative positions of the particles are determined by the trapping potential
and the Pauli exclusion principle. Measuring all particles at once, their
positions tend to be close to vertices of non-trivial polyhedrons. Similar
shapes are found for systems of particles bound to the surface of a sphere.
