There is an MSNBC story about "DNA origami", a technique invented by Paul Rothemund at Caltech to form large complicated shapes by controlling folding patterns in long DNA chains.
Each of the two smiley faces are giant DNA complexes, imaged with an atomic force microscope. Each is about 100 nanometers across (1/1000th the width of a human hair), 2 nanometers thick, and comprised of about 14,000 DNA bases. 7000 of these DNA bases belong to a long single strand. The other 7000 of these bases belong to about 250 shorter strands, each about 30 bases long. These short strands fold the long strand into the smiley face shape. - Paul Rothemund
Rothemund's work is published in Nature, and the full text is available as a PDF at his website. Rothemund works in the DNA and Natural Algorithms Group headed by Erik Winfree.