digraph Perl
{
graph [ rankdir="TB" ]
node [ shape="oval" ]
edge [ color="grey" ]
"Andromeda"

subgraph "cluster_1"
{
graph [ bgcolor="cornflowerblue" label="Locale" rankdir="TB" ]
node [ shape="oval" ]
edge [ color="grey" ]

"Solar system"
"Earth"
}
"Andromeda" -> "Solar system" [ label="" ]
"Solar system" -> "Earth" [ arrowhead="diamond" label="" ]
}