\load[tikz]

\nopagenumbers

\tikzpicture
  [grow=south, every node/.style={circle, ball color=blue, color=yellow, font=\bf}]
  \node {root}
    child {node {left}}
    child {node {right}
      child {node {ch-a}}
      child {node {ch-c}}  
      child {node {ch-b}}
    };
\endtikzpicture

\end

