The next generation of direct detection experiments will be exceptionally sensitive to dark matter (DM) induced electronic excitations in a variety of atomic, molecular, and crystal targets. Unlike nuclei in nuclear recoil experiments, electrons in these targets are heavily influenced by their environment, causing the electronic states to deviate from free, plane waves. All DM-electron phenomenology in these targets depends on understanding how DM interacts with these non-trivial electronic states. In this talk we will discuss how non-relativistic (NR) effective field theory (EFT) can be used to derive how DM interacts with electrons in any target, starting from a general high-energy interaction Lagrangian. This provides an explicit connection between any high-energy theory and its low-energy phenomenology in direct detection experiments. Furthermore we discuss the Feynman rules for the NR EFT of DM-electron interactions, which allows observables to be computed diagrammatically, and derives in-medium screening effects for any DM model.