More than half of all drugs given to patients work by targeting a particular type of "docking station," or receptor, found on body cells, to steer the cell's machinery toward healing an illness.

Scientists' inability to follow the whereabouts of cells injected into the human body has long been a major drawback in developing effective medical therapies. Now, researchers at Johns Hopkins have developed a promising new technique for noninvasively tracking where living cells go after they are put into the body.