A French and an American scientist shared a chemistry award for designing a tool to alter DNA mutations that can cause many diseases. Emmanuelle Charpentier of France and Jennifer A. Doudna of the United States won the Nobel Prize in chemistry on Wednesday for inventing CRISPR-Cas9.

What is CRISPR used for? Scientists are carrying out more than 100 clinical trials using the gene-editing tool to treat inherited diseases, said Victor Dzau, president of the National Academy of Medicine. Doctors a CRISPR cancer treatment in November and have used the method against sickle cell disease, HIV, and inherited forms of blindness. But the technology has sparked controversy, too. Experts around the world criticized Chinese scientist He Jiankui in 2018 when he he used it to try to give the first gene-edited babies resistance to the AIDS virus.

Dig deeper: Sophia Lee’s interview with bioethicist William Hurlbut about unethical uses of CRISPR.