\documentclass[10pt]{article}

\usepackage[usenames,dvipsnames]{color,xcolor}

\usepackage{tikz}

\usepackage[active,tightpage]{preview}
\PreviewEnvironment{tikzpicture}
\setlength\PreviewBorder{1mm}%




\begin{document}

\begin{tikzpicture}


\draw[](0,0)rectangle(1,1) node[midway]{1};
\draw[](1,0)rectangle(2,1) node[midway]{2};
\draw[](0,1)rectangle(1,2) node[midway]{3};
\draw[](1,1)rectangle(2,2) node[midway]{4};

\draw[-latex,red,line width=2pt](0.6,0.6)--(1.4,1.4);


\end{tikzpicture}

\end{document}