“Leonard” is the name of a new diagnostic technique based on CRISPR-Cas-9 technology. The new diagnostic test, described by an article recently published in Science, is able to detect multiple biomarkers of a disease or multiple mutations associated with specific viruses, in a single analysis. The technique is based on the discovery of a new messenger RNA, a sort of “mother RNA”, from which all the different mutations originate. In the future, this technology could revolutionize medical diagnosis, not only for infectious diseases and antibiotic resistance, but also for cancer and rare genetic diseases.