  Correlated oxide heterostructures pose a challenging problem in condensed
matter research due to their structural complexity interweaved with demanding
electron states beyond the effective single-particle picture. By exploring the
correlated electronic structure of SmTiO$_3$ doped with few layers of SrO, we
provide an insight into the complexity of such systems. Furthermore, it is
shown how the advanced combination of band theory on the level of Kohn-Sham
density functional theory with explicit many-body theory on the level of
dynamical mean-field theory provides an adequate tool to cope with the problem.
Coexistence of band-insulating, metallic and Mott-critical electronic regions
is revealed in individual heterostructures with multi-orbital manifolds.
Intriguing orbital polarizations, that qualitatively vary between the metallic
and the Mott layers are also encountered.
