Tree in a graph's node

Question

I am trying to figure out how I can draw a tree in a graph's node with tikz. Meaning, the node is not supposed to have a value or name but a tree inside of the circle around it.

I tried the following with no success:

• Insertion of qtree with \Tree [.Root[.Node Leaf] ].Root
• Insertion of a new picture in this node

Answer 1

I've no problem with tikz-qtree inside a tikzpicture inside a \node

\documentclass{standalone}
\usepackage{tikz}
\usepackage{tikz-qtree}
\begin{document}
\begin{tikzpicture}
\node[circle,draw]{\begin{tikzpicture} 
\Tree  [.S  [.NP  [.Det  the  ]  [.N  cat  ]  ]
[.VP  [.V  sat  ]
[.PP  [.P  on  ]
[.NP  [.Det  the  ]  [.N  mat  ]  ]  ]  ]  ]\end{tikzpicture}};
\end{tikzpicture}
\end{document}

Answer 2

You can add another tikzpicure in your tikzpicture and draw a tree inside of it. Below is a simple example:

\documentclass{article}
\usepackage{tikz}

\begin{document}

%start first picture
\begin{tikzpicture}
%draw a node
 \node[circle,draw] {
%add a tikzpicture in the node
\begin{tikzpicture}
\node {root}
child {node {left}}
child {node {right}
child {node {child}}
child {node {child}}
};
\end{tikzpicture}
};
\end{tikzpicture}

\end{document}