The rings in a 2D network can be conceived of as being the next level up in a hierarchy of network features: a node at an interaction site is a zerodimensional feature, an edge between two nodes is a one-dimensional feature, and the rings formed edges are two-dimensional features as shown in Figure . A ring representation of a 2D network allows for analysis of medium range order, including how those rings are correlated to one another (for example, are rings with many sides adjacent to rings with few sides or vice versa as measured by ) or characterising networks by the distribution of the rings seen in them (referred to by authors such as or Le as 'ring statistics'). Ring statistics are also used in studies of 3D networks, although the definition of a ring is less well defined and the ring structure is considerably harder to visualise. The most intuitive set of 3D features to treat with a persistence diagram are pores in zeolites as discussed by , although those are outside the scope of this work.