The five-month-old boy has the usual DNA from his mum and dad, plus a tiny bit of genetic code from a donor.
US doctors took the unprecedented step to ensure the baby boy would be free of a genetic condition that his Jordanian mother carries in her genes.
Experts say the move heralds a new era in medicine and could help other families with rare genetic conditions.
But they warn that rigorous checks of this new and controversial technology, called mitochondrial donation, are needed.
