 Microscopic images, whether hand-drawn, as they were in the nineteenth century, or captured in photographs, are highly detailed. However, the knowledge cytologists and cell biologists seek to develop is more abstract and general—they seek to identify the types of structures found in cells, not all their instances. Accordingly, cell biologists frequently generate diagrams that leave out details. Maienschein (1991) examines the origin of this practice in Wilson’s (1896) classic text, The Cell in Development and Inheritance. Early in the book Wilson provided a diagram  (Figure 5A)  which abstracts from the much more replete photographs he had presented just a year earlier (Wilson 1895). Instead of showing all the instances of different organelles, he presents just a few instances of each type. Organelles are shown using icons that are suggestive of their shapes. Such diagrams serve to convey the types of organelles found in cells and their typical location, but falsely suggest that most of the space in the cell is empty. Maienschein contends that this transition from photographs to abstract diagrams reflects Wilson’s growing confidence in the correctness of his interpretation of what he was seeing through the microscope and a transition “from presenting data to representing theory” (Maienschein 1991: 252). A sign of their theoretical status is that such figures, unlike micrographs or data plots, often undergo numerous revisions as scientists develop their account. Revising these diagrams is a means, in fact, of developing theory. With the development of biochemical and molecular accounts of cell phenomena, researchers often make what Serpente (2011) characterizes as a transition from the iconic to the symbolic. He presents protein-protein interaction maps and gene regulatory diagrams as examples of symbolic representations.