digraph Perl
{
graph [ rankdir="TB" ]
node [ shape="oval" ]
edge [ color="grey" ]
subgraph "cluster_1"
{
graph [ bgcolor="lightblue" label="Creatures" rankdir="TB" ]
node [ shape="oval" ]
edge [ color="grey" ]
"Great"
"Small"
}
"Great" -> "Small" [ arrowhead="odot" label="" ]
}