It's no exaggeration to say the gene-editing technique CRISPR could revolutionize medicine. We look at a new milestone — a CRISPR treatment that edits a patient's DNA while it's still inside their body. NPR health correspondent Rob Stein explains how, if this treatment works, it could open up new avenues of treatment for diseases, like a genetic form of blindness, that were previously off limits to CRISPR.
