A reall small smiley face:

A nanotechnologist has created the world's smallest and most plentiful Smiley, a tiny face measuring a few billionths of a meter across that is assembled from strands of DNA.

Fifty billion Smileys, each a thousand times smaller than the diameter of a human hair, can be made at a stroke under the technique pioneered by Paul Rothemund at the California Institute of Technology (Caltech).

While seemingly trivial, the technique holds great promise for the manufacture of nano-scale computers and novel methods of drug delivery.