High-T_c superconductors with CuO ₂ layers, manganites La _1-x Sr _x MnO ₃ and cobaltites LaCoO ₃ present several mysteries in their physical properties. Most of them are believed to come from the strongly-correlated nature of these materials. From the theoretical viewpoint, there are many hidden rocks in making the consistent description of the band structure and low-energy physics starting from the Fermi-liquid approach. Here, we discuss the alternative method — multielectron approach to the electronic structure calculations for the Mott insulators — called LDA + GTB (local density approximation + generalized tight-binding) method. Its origin is a straightforward generalization of the Hubbard perturbation theory in the atomic limit and the multiband p-d Hamiltonian with the parameters calculated within LDA. We briefly discuss the method and focus on its applications to cuprates, manganites and cobaltites.