DescriptionWhat is non-fundamental reality like? What sorts of connections stretch from the fundamental up through the non-fundamental? In this dissertation, I take some preliminary steps towards developing a complete, unified theory of non-fundamentalia. I focus, in particular, on theories of explanation for non-fundamental phenomena. In the first chapter, I argue that there is a single `explanatory determination' relation which (i) backs all cases of explanation among fundamentalia and non-fundamentalia alike, and (ii) explains why all other explanation-backing relations are explanatory. In the second chapter, I argue that typicality facts---for instance, the non-fundamental fact that gases typically evolve to equilibrium---can be explanatory. In the third chapter, I propose an account of what it takes for one mathematical proof to be at least as explanatory as another.