For generations, medicine has dreamed of sending small devices into the body to listen, measure, and heal from within — yet the question of how to power such devices safely has remained unanswered. Researchers have now created a battery made from paper and edible materials that dissolves harmlessly in the digestive tract, leaving no toxic residue behind. This quiet breakthrough removes one of the last fundamental barriers between the promise of ingestible medicine and its clinical reality, opening a path toward devices that can monitor, diagnose, and treat conditions deep inside the human body