Accurate and affordable simulation of how molecules and materials interact with light remains one of the greatest challenges in theoretical chemistry. Modeling photochemical reactions requires quantum mechanical description of the electronic structure in ground and excited electronic states. Despite significant advances in quantum chemistry, most of the available electronic structure methods for accurate simulations of excited states are computationally very expensive and have limited applications. In this talk, I will describe our group’s research on the development of new methods for the spectroscopic simulations of molecules and materials using the framework of algebraic diagrammatic construction (ADC) theory. The ADC approach strikes a careful balance between computational accuracy and efficiency by calculating excited-state energies and electronic spectra from a linear-response function approximated by low-order perturbation theory. In the first half of my talk, I will briefly outline the theoretical foundations of ADC and demonstrate its calculations of charged excited states and photoelectron spectra of molecules and materials. In the second half, I will present a new formulation of ADC called multireference ADC that enables accurate spectroscopic simulations of molecules with complicated electronic structure. I will conclude my talk by outlining the prospects for future developments of this theoretical approach.