This special issue moves beyond an understanding of diagrams as mere inscriptions of objects and processes, proposing instead to re-evaluate diagrammatic reasoning as the work that is carried out with, on, and beyond diagrams. The introduction presents this issue’s focus on ‘working with diagrams’ in a way that goes beyond semiotic, cognitive, epistemic, or symbolic readings of diagrams. It discusses recent research on diagrams and diagrammatic reasoning across disciplines and approaches diagrams as suspended between imagination and perception—as objects with which work is done and as objects that do work. Contributions to this issue probe diagrams for the work they do in the development of disciplinary theories, investigate their reworking of questions of time and scale, and ask how some diagrams work across fields and disciplines. Other authors shift the perspective to their own work with diagrams, reflecting on the practice and performative nature of diagrammatic reasoning in their respective fields and disciplines.