From Ana Lopes at Physics:
Electronic tags in the form of radio-frequency identification (RFID) devices are everywhere. They show up in key cards, e-passports, toll passes, you name it. H.-S. Philip Wong, Ada Poon, and colleagues at Stanford University, California, have now made an RFID tag that is small enough to be placed inside a cell. Such tags might one day be used to track and monitor individual cells wirelessly. Paper. (paywall) More.
Tracking cells should help us understand more of the specified complexity of life.
See also: Tiny molecular machines that keep chromosome numbers correct have been identified