It is crucial to any simulations to find a trade-off between accuracy and computational demand. On one side, continuum models, e.g. finite elements, provide a flexible and relatively affordable description of matter at the macroscale. On the other hand, however, such models do not take into account the natural discretization of Nature, namely atoms. Thankfully, in many cases, the atomistic description of a material, which is computationally expensive, is needed only in some spatial region. Building models that effectively bridge these two level of accuracy would enable accurate yet affordable simulations of complex devices.