The achievements for hybrid DFT simulations demonstrated above is a big success and paves the way to efficient use of exa-scale resources in the future. Still, the accuracy of hybrids is limited by construction. The required fraction of exact exchange is an open point. A related question is the treatment of the electron correlation -hybrid density functionals addressing this point only insufficiently. Approaches using range-dependent parameters for the fraction of exact exchange or double hybrids are a way forward to improve the accuracy of the ab initio model. The GW approach and the CCSD method provide much more accurate access to electronic structure quantities per se, but the complexity of these methods will limit their application to smaller system sizes for the foreseeable future.