Here’s what you’ll learn when you read this story:The first babies with three biological parents were born out of a new technique to prevent mitochondrial disease. The nucleus of an egg fertilized in vitro was transferred into a donor egg without a nucleus, but with viable mitochondria. Eight healthy babies, including a set of twins, were born with low to undetectable levels of mitochondrial mutations. They were previously only preventable by using a donor egg or foregoing the conception of biological children altogether. Levels of defective mitochondria in offspring conceived via pronuclear transfer were low enough to escape that fate.