A composition of microscopic devices utilizable in a medical diagnostic or therapeutic procedure. Each microscopic device includes a nanostructure provided with a ligand for effectively coupling the nanostructure to a predetermined chemical or molecular site. A medical method in part comprises inserting the medical devices into a patient, attaching the nanostructures via the respective ligands to instances of a predetermined type of target structure inside the patient, and thereafter activating the nanostructures to perform a preselected medical diagnostic or therapeutic function.