We discuss interaction effects in Dirac materials. In a first part I will discuss the role of interaction in graphene and manifestations of interactions in transport measurements in weakly interacting systems. For strong interactions for a concrete phenomenological model we will also discuss the quantum critical conductivity of graphene at a semimetal-to-insulator transition (breaking the chiral symmetry) and make connection to experiments conducted on suspended graphene samples. In a second part we discuss topological insulators and specifically the Dirac character of surface states. We argue that upon driving a bulk quantum phase transition surface states can be tuned in a way which might facilitate the observation of chiral symmetry breaking on the surface.