Behind this simple grin is one of the most complex nanostructures ever made. To construct this 100-nanometer-wide smiley face, computer scientist Paul Rothemund of the California Institute of Technology in Pasadena improved on a technique known as DNA origami.
In it, a single-helix strand of synthesized DNA is folded into a loose geometric shape and held in place with a few short strands of DNA. By weaving many more short "staple strands" of DNA into the long strand's scaffold, Rothemund bound the DNA into a tight, mazelike pattern. With this technique, he created several shapes that are "10 times as complex and several times bigger" than previous DNA origami designs, Rothemund reports in the March 16 Nature.