More than 100 years ago, German Nobel laureate Paul Ehrlich popularized the ‘magic bullet’ concept — a method that clinicians might one day use to target invading microbes without harming other parts of the body. Although chemotherapies have been highly useful as targeted treatments for cancer, unwanted side effects still plague patients. Now, researchers have demonstrated that specialized nucleic acid-based nanostructures could be used to target cancer cells while bypassing normal cells.