\documentclass{standalone}
\usepackage{tikz}
\tikzset{inner sep=0pt, outer sep=0pt}
\begin{document}
\begin{tikzpicture}
\foreach \x in {1,...,900} {
  \pgfmathparse{rnd*100} \let\malx=\pgfmathresult
  \pgfmathparse{rnd*100} \let\maly=\pgfmathresult
  \node[xshift=\malx mm, yshift=\maly mm, circle, fill, minimum width=1mm]{};
} % end of \foreach \x
\end{tikzpicture}
\end{document}