\begin{tikzpicture}[
	scale=1.0,
	fine/.style={circle,draw=black,thick,inner sep=2},
]

\draw[step=1.0,black] (0.75,0.75) grid (6.25,6.25);
\draw[step=0.5,gray,thin] (2,2) grid (5,5);

\foreach \x in {0,...,6}
	\foreach \y in {0,...,6}
		\node[fine] at (2+0.5*\x,2+0.5*\y){ };
\end{tikzpicture}