As is commonly known, one of the hot topics in physics is the search for the unification of quantum (field) theory and general relativity theory. If successful, the famous “Theory of Everything” would result. As is equally well-known, the hardest problem to solve is how to deal with space-time. Quantum (field) theory requires space and time as a background, whereas in general relativity the structure of space-time is largely determined by the masses and the energy present.  One way out—and most of section 3 deals with such examples—is to find a “deeper” structure that underlies both theories and that, in a sense, generates space and time from more fundamental concepts. Clearly, if such a theory were to be found, it would not merely produce “just” a model, but it would actually be considered as a genuine representation of reality. Most of these models, speculative as some of them may be at the present moment, turn out to be discrete and hence these proposals, in contradistinction, e.g., with the logicians, do claim to be a correct description. For a recent informal overview, see Rovelli (2016), especially chapter 11, “The End of Infinity”.