 Why are philosophers interested in fundamentality? One reason comes from a certain view of science. It is not uncommon to think that particle physics has some special role in our inquiry into the structure of reality. After all, every material entity is made up of fundamental particles. So, one might think that particle physics aims to describe the fundamental level of reality, which contains the basic building blocks of nature. We can then employ the notion of relative fundamentality, which enables us to express the hierarchical nature of reality disclosed by science, according to which the facts of biochemistry depend on the facts of elementary chemistry, which depend in turn on the allegedly fundamental facts of fundamental particle physics.