Dense granular materials provide a rich setting to explore networks and topology. Of particular interest here are states near the jamming transition. The idea of jamming is simple: if a collection of grains is too loose, then it will not be mechanically stable. If it is very dense, there will be more than enough force-bearing contacts to make the system stable or jammed. The concept of states that are marginally stable is then a natural one. Until recently, it was thought that density alone controls the jamming transition.