\setlength{\unitlength}{0.5cm}
\renewcommand{\axeslabelsize}{\footnotesize}
\begin{Picture}(-5.5,-4.5)(5.5,4.5)
\cartesiangrid(-5,-4)(5,4)
\pictcolor{blue}
\Ellipse{4}{3}
\Circle{2}
\end{Picture}

\referencesystem(0,0)(1,0)(0.5,0.5)
\begin{Picture}(-5.5,-4.5)(5.5,4.5)
\cartesiangrid(-5,-4)(5,4)
\pictcolor{blue}
\Ellipse{4}{3}
\Circle{2}
\end{Picture}
