CRISPR genome editing is a revolutionary technology that can be used to make highly targeted changes in DNA in living cells. JAMA Associate Editor W. Gregory Feero, MD, PhD, Maine Dartmouth Family Medicine Residency, and Matthew J. Kan, MD, PhD, University of California San Francisco, discuss how CRISPR works and how CRISPR-based technologies are being used in ongoing trials to treat a wide variety of medical conditions. Related Content: Treatment of Genetic Diseases With CRISPR Genome Editing With First CRISPR Trials, Gene Editing Moves Toward the Clinic