In the context of all of these approaches, the focus of this topical review is specifically on embedded Many-Body Green's Function methods, that is, calculations using GW -BSE as the high-accuracy electronic structure method for a region of interest embedded into a region at lower-level description. As we will see, there are generally two classes of embedding strategies here: one is treating GW -BSE just as any other high-level method and couple it extrinsically to the lower-level method via, e.g., in the case of only weakly interacting systems purely classical electrostatic interaction modules. While very powerful, as we will discuss in detail in Section 3.3, GW -BSE also allows for another class of approaches. These exploit the fact that one of the main ingredients of the Green's functions methods here is the screened Coulomb interaction, W , which is essential for representing the electronic many-body effects in quasiparticle and electronhole excitations. In some sense, GW -BSE can be seen as an exciting merger between advanced quantum-mechanical principles, on the one hand, with classical electrostatic concepts, on the other hand. Embedding approaches can be devised that explicitly and intrinsically make use of these electrostatic concepts at the core of GW -BSE.