 Similar points also apply to another type of diagram that appears frequently in cell biology—diagrams of hypothesized mechanisms that are taken to be responsible for a particular phenomenon (Sheredos et al. 2013; Abrahamsen, Sheredos, &amp; Bechtel 2018). Such diagrams do not try to show all the organelle types but, as in  Figure 5B,  only those thought to be involved in generating a particular phenomenon—in this case, the breakdown of materials taken into the cell (heterophagy) or of cell components themselves (autophagy). One challenge with mechanism diagrams is that they are static whereas mechanisms are engaged in change (the digestion of organelles and the expulsion of the remaining material). One common strategy is to use arrows to represent activities, although often within the same diagram arrows may have multiple different meanings. Ultimately, however, it is up to the viewer to animate a mechanism diagram (Hegarty 1992)—to rehearse mentally the different activities that are represented and to imagine the changes that are being produced by different parts.