3D hybrid perovskites (HOP) are currently superstar materials for photovoltaics and attract increasing attention of the scientific community. Recently, they also revealed attractive photoluminescence, as it is already well known for 2D layered HOP. Our modelling approach is based on concepts of solid-state physics originally developed for conventional semiconductors and nanostructures, mixing both DFT and empirical modelling. The broad light-harvesting abilities and attractive transport properties of 3D HOP can be related to the multi-bandgap and multi-valley nature of their band structure. Giant spin-orbit coupling in the conduction band is a specific property of this new class of semiconductors. Perturbations related to lattice distortion and loss of inversion symmetry at low temperature, are studied. Concept of Wannier exciton is reviewed for both 3D and 2D layered HOP. A novel approach for dielectric confinement will be described. Concepts of quantum confinement and applicability of effective masses coupled to envelope functions are analyzed for 3D heterostructures and 2D layered HOP.