SmB6 is under focus because it may be the first topological insulator that is also strongly correlated. It is intermediate valent and a gap opens only at low temperatures due to an intricate interplay between correlation effects and hybridization, yet the surface is always conducting. The topological properties of the surface are determined by the bulk so that it is surprising that the bulk crystal-field ground state of Sm3+ was unknown until now despite many attempts by e.g. neutron scattering. Recently, scientists from the Max-Planck Institute for Chemical Physics of Solids and the University of Cologne clarified this issue by applying a new technique, namely core-level non-resonant inelastic x-ray scattering, see Sundermann et al., Phys. Rev. Letter 120, 016402 (2018). The finding that the ground state is the Γ8 quartet and not the Γ7 doublet, contradicts all existing band structure calculations and illustrates in a sobering manner the difficulties in making reliable predictions for the properties of correlated systems.