Hello All, I need a graph structure as follows. (Here my input is a Graph which I call it as " Control Flow Graph".) On this "Control Flow Graph", I run a algorithm it creates another graph, and on that I will run again the algorithm, it will create another "Graph" and it continues until it become a "Single Node". I should be able to access all the Graphs in each stage and my original graph information should be untouched. What is the best way to do it ? Any suggestions ? (Actually, I am trying to solve one problem using "Interval Based Analysis" of Control Flow Graphs. I would like to divide the given main control flow graph into disjoint intervals. You can have a look at the following link for more information http://nptel.iitm.ac.in/courses/106108052/module9/control-flow-ana-2.pdf ) Regards, Srinivas