I want to create math font inside of my vertex circles, AND draw edges between them. How I typically create network graphs is as follows:
\usepackage{tkz-graph}
\begin{tikzpicture}
\Vertex[x=1,y=6]{A};
\Vertex[x=1,y=5]{B}
\Vertex[x=1,y=4]{C}
\Edge[label= 20](B)(C)
\end{tikzpicture}
However, if I do the following, it doesn't work. How can I get around this so that I can have equations or math font inside my nodes and connect them with an edge?
\begin{tikzpicture}
\Vertex[x=1,y=6]{$\frac{x}{y}$};
\Vertex[x=1,y=5]{$2^n$}
\Vertex[x=1,y=4]{$t$}
\Edge[label= 20]($2^n$)($t$)
\end{tikzpicture}

[Math]option and\SetVertexMathswitch. – percusse Jan 29 '13 at 02:35