Research and industry are increasingly exploiting the potential of aptamers. As well as their application in research, medical diagnosis and treatment, aptamers are also interesting as a basis for biosensors for use in environmental analysis because their characteristics enable them to identify and bind target molecules as surely as a key fits a lock. In a new book, researchers at the Helmholtz Centre for Environmental Research (UFZ) describe the methods used to obtain aptamers. A newly-approved project aims to develop new nanostructured biosensors to measure harmful substances in water.