Mereological nihilism is the thesis that composition never occurs. Some philosophers have thought that science gives us compelling evidence against nihilism. In this article I respond to this concern. An initial challenge for nihilism stems from the fact that composition is such a ubiquitous feature of scientific theories. In response I motivate a restricted form of scientific anti-realism with respect to those components of scientific theories which make reference to composition. A second scientifically based worry for nihilism is that certain specific scientific phenomena (quantum entanglement, natural selection) might require ineliminable quantification over composite objects. I address these concerns, and argue that there seem to be nihilist-friendly construals of the scientific phenomena in question.