For some time now, scientists have been experimenting with the use of lasers to control the expression of particular genes within living bodies without the invasiveness of wires or electric shocks. But "optogenetics" first required the insertion of special photosensitive genes, which made the technique unusable in humans.
Now a group of Spanish scientists has nanoengineered a pair of peptides—a kind of protein—that also change shape predictably in reaction to light. These "traffic light" peptides can be used to stop and start traffic across cell membranes. One day, as part of the future of "personalized medicine," this technique could be used to develop medicines that destroy tumors or disease in delicate areas of the body without causing side effects or damaging surrounding tissue.