Nanoscientists have fashioned DNA into all manner of interesting shapes, from cubes to smiley faces. But a practical use for such structures has remained elusive—until now. A team led by Andrew J. Turberfield of Oxford University reports that tetrahedral cages of DNA can penetrate live mammalian cells, suggesting they could be used to deliver drugs and imaging agents (ACS Nano, DOI: 10.1021/nn2005574). Turberfield’s team found that fluorescently labeled DNA tetrahedra assembled from four 63-nucleotide chains (shown) can slip into human embryonic kidney cells with or without the help of a transfection agent. After penetrating the cells, the DNA cages remain largely intact in the cytoplasm for at least 48 hours, experiments show. “These results represent an important first step as proof of concept in efforts to use DNA cages to deliver cargoes and to control their activities within cells,” the researchers note.