So far, in all our recipes, we have dealt with static graphs. Static graphs are those graphs in which the nodes as well as the edges are fixed and do not change over time. In other words, the system that is represented by these graphs changes neither its entities nor the relationships between them over time. Also, the graphs that we've dealt with were all single-level graphs. That is, the relationships present between the entities didn't possess any hierarchies.

In this chapter, we are going to dive into two special kinds of graphs: dynamic graphs and multilevel graphs. These graphs come in handy while representing the real-world systems that keep changing with time and where the relationships among entities are much more complex.