My main current interest centers on understanding the source of hierarchy in real-world networks and modeling biological growth. I believe that hierarchy emerges as the result of all network models being a course-graining of some more complex network of systems of systems. For example, in a social network, nodes are people, but really each person could be modeled (whether correctly or not) as a complex network of neurons. The conductance, or limit on information flow, of these sub-networks should lead to restrictions on the flow through each node in the course-grained model, which may manifest as degree limits. Hierarchy then naturally emerges to allow for efficient dissemination across the network.