\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage[english,greek]{babel}

\usepackage{tikz}
\begin{document}
Βλέπε εικόνα~\ref{fig1}.

\begin{figure}
\centering
\begin{tikzpicture}
%\resizebox{\textwidth}{!}{
\draw[step=0.5cm,gray,very thin] (-2,-1) grid (2,4);
\draw[->] (-2.2,0) -- (2.2,0) node[right] {$x$};
\draw[->] (0,-1) -- (0,4.2) node[left] {$y$};
 \foreach \x in {-2, -1, 1, 2}
     \draw (\x,0) -- (\x, -0.1) node[below] {\x};
 \foreach \y in {1, 2, 3, 4}
     \draw (0,\y) -- (-0.1,\y) node[left] {\y};    
 \draw[scale=1, domain=-2:2, smooth, variable=\x, blue, 
      thick]
      plot ({\x}, {pow(\x,2)}) node[right] {$y=x^2$};
\end{tikzpicture}
%}
\caption{Συνάρτηση $y=x^{2}$}\label{fig1}
\end{figure}
\end{document}
