What justifies the allocation of funding to research in physics when many would argue research in the life and social sciences may have more immediate impact in transforming our world for the better? Many of the justifications for such spending depend on the claim that physics enjoys a kind of special status vis-a-vis the other sciences, that physics or at least some branches of physics exhibit a form of fundamentality. The goal of this paper is to articulate a conception of fundamentality that can support such justifications. I argue that traditional conceptions of fundamentality in terms of dynamical or metaphysical completeness rest on mistaken assumptions about the nature and scope of physical explanations.