Forget GMO. Get ready for GMH. CRISPR, the genome-editing technology that has taken biomedical science by storm, is finally nearing human trials. On 21 June, an advisory committee at the US National Institutes of Health (NIH) approved a proposal to use CRISPR–Cas9 to help augment cancer therapies that rely on enlisting a patient’s T cells, a type of immune cell. Where some gene modification techniques have involved the brute-force insertion of genetic material (including shooting at cells with an air pistol), CRISPR is a much more exacting technique that offers multiple approaches to carefully editing genes, including human genes. What CRISPR offers, and biologists desire, is specificity: the ability to target and study particular DNA sequences in the vast expanse of a genome.