CRISPR-Cas9 is a molecular system that scientists discovered can be used to edit DNA.
The Cas9 enzyme, shown here in blue, both recognizes and cuts only a specific, target region of DNA. That DNA can then either be repaired with or without guidance, leading the deactivation of a gene or the insertion of a new gene.
Illustration by Falconieri Visuals for a feature on the Kavli Prize winners in Scientific American, January 2020. Also available online: The Long View On Gene Editing.