This chapter offers an overview of Engels’ overall undertaking in Dialectics of Nature, underscoring different stages of his work between 1873 and 1886. It goes against the grain of classical readings that presume a single ‘book’ or a single project. It argues that Dialectics of Nature consists of seven projects, with three larger and four smaller plans. Engels does not seem to have completed any of these projects. He rather left behind a lengthy metacommentary on philosophy and natural sciences. In the entire writing process, Engels largely works with two parameters of opposition: metaphysics versus dialectics and idealism versus materialism. The theoretical arena in which he defends dialectics and materialism against metaphysics and idealism is shaped by a third pair of opposites which he tries to overcome: natural sciences versus philosophy. Engels’ orientation is intimately tied to a key problem that is usually called ‘application of dialectics to nature’.