A magnet is a bitter pill to swallow. But now, pills filled with magnets and tiny sensors have given scientists a high-resolution map of the forces exerted on food and medicine traveling through the guts, researchers report today in the Proceedings of the National Academy of Sciences. For the first time, researchers can accurately calculate the digestive system's strongest force, which happens when food empties from the stomach into the small intestine, as roughly equivalent to a single grape smashing into the ground. They can use this knowledge to design pills that counteract the emptying force and stay longer in the stomach, allowing the absorption of more medicine. The research may also be used to diagnose and treat irritable bowel syndrome, acid reflux, and other gastrointestinal disorders.