History of science's spatial turn has focused on the horizontal dimension, leaving the role of the vertical mostly unexplored as both a condition and object of scientific knowledge production. This special issue seeks to contribute to a burgeoning discussion on the role of verticality in modern sciences, building upon a wider interdisciplinary debate about the importance of the vertical and the volumetric in the making of modern lifeworlds. In this essay and in the contributions that follow, verticality appears as a (...) condition of knowledge production—a set of movements and mobilities, technical challenges, political negotiations, and bodily hardships—and an object of scientific inquiry, requiring new techniques of mapping and visualisation and generative of new insights into physical processes and temporal change. By foregrounding the vertical, historians of science can gain new insights and tell new stories about how science is done in the field, the observatory, and the laboratory, and about how those sciences have helped build a modern, three-dimensional world. (shrink)