\documentclass{article}
\usepackage[utf-8]{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}