documentclass{book}
usepackage{pgf}
usepackage{tikz}
usetikzlibrary{shapes,external}
tikzexternalize
usepackage{lipsum}
tikzset{naming/.style={align=center,font=footnotesize}}
tikzset{area/.style = {draw, shape = regular polygon, regular polygon sides = 6, thick, minimum width = 5cm}}
begin{document}
lipsum[2]

include{tikzcode}

lipsum[2]
end{document}

begin{figure}[htb]
centering
begin{tikzpicture}[font=footnotesize]
node [area] at (0,0) (cell1) {};
end{tikzpicture}
caption{test}
label{fig:test}
end{figure}