The flexible properties of hydrogels, which shrink or expand depending on their environmental, have made them ideal for many applications, from contact lenses to baby diapers and adhesives. Recently, scientists at the Massachusetts Institute of Technology have been investigating hydrogels' potential in drug delivery, engineering them into drug-carrying vehicles that rupture or change shape when exposed to certain environmental stimuli. The vesicles could allow for the controlled release of drugs or may even contain more than one type of drug, each released under various conditions.