How do I create very small shapes?

Question

I'd like to draw multiple very small shapes. But there seems to be a minimum size of approx. 3mm (for circles) if I use minimum width to change the size.

Is there a simple way to create smaller shapes?

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{shapes}
\begin{document}

\begin{tikzpicture}
\foreach \x/\y in {0/1,1/2,2/3,3/4}
    \node[circle, draw,minimum width=\y mm, label={90:\y mm}] (c\x) at (\x,0){};
\end{tikzpicture}

\end{document}

Answer 1

Set inner sep=0pt:

\documentclass{article}
\usepackage[utf8]{inputenc}
\usepackage{tikz}
\usetikzlibrary{shapes}
\begin{document}

\begin{tikzpicture}
\foreach \x/\y in {0/1,1/2,2/3,3/4}
    \node[inner sep=0pt,circle, draw,minimum width=\y mm, label={90:\y mm}] (c\x) at (\x,0){};
\end{tikzpicture}

\end{document}