Molecular para-hydrogen cluster with N=5 molecules. Each hydrogen molecule is represented by a rigid rotor or dumbbell. The five green dumbbells represent one possible realization or snapshot (similarly for the blue and red dumbbells). The light green sphere illustrates the ``size'' of the N=5 cluster, which is defined here so that 95% of the hydrogen molecules are contained in the corresponding volume. Clearly, molecular para-hydrogen clusters are highly diffuse quantum objects for which a classical description is insufficient.