We will cover how an electronic excited state can be computed within the orbital based methods used in ground state chemistry. We cover symmetry, spin and orthogonality constraints. An overview of CIS methods (TD-DFT, etc.) and CASSCF methods is given. Dynamical correlation are introduced and we can explore the need of multi-reference theories. The last part leads us beyond the Jablonski Diagram – potential energy surfaces for excited states.