Graphene has unique electronic properties that arise from its 2D honeycomb structure and which cause novel behavior at the atomic scale.This can be seen in graphenes response to charged impurities, where graphenes ultra-relativistic nature leads to impurity states that are unlike those found in any other material.We have explored such impurity states across different impurity-charge regimes by building charge centers (i.e.,"artificial nuclei") atom-by-atom at the surface of graphene devices and probing them via scanning tunneling microscopy.New results on this topic, including the observation of "atomic collapse" [1], will be discussed.