\documentclass{article}
\usepackage{tikz}
\usetikzlibrary{arrows}
\usetikzlibrary{snakes}
\usetikzlibrary{positioning}

\usetikzlibrary{calc}
\usepackage{verbatim}

\tikzstyle{mybox} = [draw=red, fill=blue!20, very thick,
    rectangle, rounded corners, inner sep=10pt, inner ysep=20pt]

\begin{document}

\begin{tikzpicture}[scale=1.5]



%\foreach \x in {0,...,5}
%    \fill[ball color=red] (\x,0,0) circle (0.05);

%\foreach \x in {0,...,5}
%    \fill[ball color=red] (\x,1,0) circle (0.05);
    
%\foreach \x in {0,...,5}
%    \fill[ball color=red] (\x,2,0) circle (0.05);    

%\foreach \x in {0,...,5}
%    \fill[ball color=red] (\x,3,0) circle (0.05);    
    
%\foreach \x in {0,...,5}
%    \fill[ball color=red] (\x,4,0) circle (0.05);    

%\foreach \x in {0,...,5}
%    \fill[ball color=red] (\x,5,0) circle (0.05);    

%\foreach \y in {0,...,5}
%    \fill[ball color=red] (0,\y,0) circle (0.05);

%\foreach \y in {0,...,5}
%    \fill[ball color=red] (1,\y,0) circle (0.05);

\foreach \x in {0,...,3}
    \foreach \y in {0,...,3}
        \foreach \z in {0,...,3}
            \fill[ball color=gray] (\x,\y,-\z) circle (0.05);
    


%\fill[ball color=red] (3,3,2) circle (0.05);
%\fill[ball color=red] (0,0,0) circle (0.05);

%    \draw[color=gray, style=thin] (0,0,0) -- (1,0,0);
%    \draw[color=gray, style=thin] (0,0,0) -- (0,1,0);
%    \draw[color=gray, style=thin] (0,0,0) -- (0,0,-1);
%    \draw[color=gray, style=thin] (0,1,0) -- (1,1,0);
%    \draw[color=gray, style=thin] (1,0,0) -- (1,1,0);
%    \draw[color=gray, style=thin] (1,0,0) -- (1,0,-1);
%    \draw[color=gray, style=thin] (1,1,0) -- (1,1,-1);    
%    \draw[color=gray, style=thin] (1,0,-1) -- (1,1,-1);  
%    \draw[color=gray, style=thin] (0,0,-1) -- (1,0,-1);
%    \draw[color=gray, style=thin] (0,1,0) -- (0,1,-1);
%    \draw[color=gray, style=thin] (0,0,-1) -- (0,1,-1);
%    \draw[color=gray, style=thin] (0,1,-1) -- (1,1,-1);
    
%    \draw[color=blue, style=thin] (1,0,0) -- (2,0,0);
%    \draw[color=blue, style=thin] (1,0,0) -- (1,0,-1);
%    \draw[color=blue, style=thin] (2,0,0) -- (2,0,-1);

\end{tikzpicture}
\end{document}