Worried about mice in the kitchen? Fed up with pigeons on your way to work? Teed off by weeds on your lawn? Recent work points to a way that might just reduce — or even eliminate — unwanted species in a short period. The method is based on something called a gene drive — a method of making changes to an entire population of a specific species by altering its genetic material. Using gene drives also carries risks. Removing a species from its environment could have unforeseen environmental consequences, or organisms could become resistant to the gene drive — instantly removing all of its advantages. Gene drives authorised in one country could also spread to countries that didn’t want it. The problem is that there is currently no way to control a gene drive once it has left the lab. But new research elaborates on how we could control gene drives to throw on the brakes and even reverse their effects.