High resolution X-ray spectroscopy is a powerful tool to probe properties of materials. Resonant scattering processes such as resonant inelastic X-ray scattering (RIXS) are techniques that allow one to characterize electronic and vibrational structures of molecules in both gas and liquid phases. In this seminar I present the theoretical approaches used to model RIXS spectroscopy in recent applications. Particularly, it will be discussed how the concept of detuning can be explored to control the quantum nuclear dynamics of excited states.