The art of the fold

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.