This is a history of medicine that takes its point of departure in the specimens of human bodily material used to produce medical knowledge. An ordering principle of scale prompts a material and epistemic history of 18th-21st century medicine that highlights shifts in interest towards smaller and smaller units of study: from organs in pathological collections, over microscope slides, to samples in biobanks. The account reveals a set of connected scales of the site of disease, time of diagnosis, size of cohorts, number of disease categories, and technologies of investigation. Moreover, the principle of following the scale of specimens demonstrates the continued importance of physical specimens in medicine, it synthesizes studies of important epistemic objects of medicine such as the organ specimen, the microscope slide and the blood sample, and it draws new historical connections from pathological collections to biobanks.