Artificial two-dimensional (2D) materials, such as graphene or single-layer transition metal dichalcogenides, permit the realization of massless and massive Dirac fermions. A special feature of the 2D materials is that their electronic properties, for instance their band gap, can be strongly influenced by either their dielectric environment or by the excited carrier density in the material. Here we exploit this to achieve a static and dynamic change in the electronic properties of 2D materials such as graphene and single layer WS2. We also make use of the electronic structure’s tunability in order to address some fundamental questions concerning the electronic self-energy in solids.