This is a small diagram I put together using the wonderful [GraphViz](https://www.graphviz.org/). The nodes in this graph denote categories of object, while an arrow $A \to B$ denotes some kind of "inclusion" of categories.
(More precisely, it denotes the existence of a forgetful functor from $B$ to $A$, so perhaps I should reverse the arrows!)
@import "math.gv"