From typogrphy.com: Atoms & Aldus.

Last week I mentioned the atomic pen, which scientists used to construct some awfully tiny letters one atom at a time. These are small letters indeed: measuring two nanometers in height, they’re about 1/40000 the thickness of a human hair, which surely gives their inventor sufficient authority to issue the casual throwdown that "it’s not possible to write any smaller than this." But it is, of course, and the technique for doing so has been known to typefounders for more than five hundred years. [continue]