digraph D {

  subgraph cluster_p {
    label = "Parent";

    subgraph cluster_c1 {
      label = "Child one";
      a;

      subgraph cluster_gc_1 {
        label = "Grand-Child one";
         b;
      }
      subgraph cluster_gc_2 {
        label = "Grand-Child two";
          c;
          d;
      }
    }
    subgraph cluster_c2 {
      label = "Child two";
      e;
    }
  }
}