 The second strand of historical epistemology identified by Feest and Sturm in their introduction to the special issue focuses on the trajectories of the objects of research—“epistemic things”—rather than on concepts, and here the well-known work of Rheinberger (1997, [2006] 2010a, [2007] 2010b) is emblematic. Renn (1995, 2004) represents the third approach, an attempt to understand the longer-term dynamics of science. For example, Renn attempts to solve several mysteries about how Einstein was able to accomplish the relativity revolution. His answer takes into account the long history of developments in distinct fields that Einstein was able to bring together, partly because of his wide philosophical and other cultural interests. Renn looks at long-term developments by analogy with biological development. Norton Wise (2011) also brings biological metaphor into play. He observes that historical narrative as a form of explanation is now making serious incursions into physics, in the physics of complex or highly nonlinear systems.  “Covering law” explanations are not available there, he says, and sometimes we must resort to simulations in order to understand how systems evolve. “We know what we can grow”.