Nanoprobe

Nanoprobes are the microscopic nanotechnology used by the Borg to assimilate new drones and maintain existing drones systems. The nanoprobes are injected into a target's bloodstream by a drone using their assimilation tubules, and the nanoprobes immediately begin to take over the bodies functions. Each drone's nanoprobes are also encoded with a unique sequence. (ST: Voyager: "Scorpion, Part II" and "One")

Nanoprobes can also be modified for a variety of medical of technical tasks, and have also been modified for warfare. In 2374, the USS Voyager discovered that the Borg were at war with Species 8472, and they were caught in the middle as they had to cross Borg space. When Harry Kim was attacked by a Species 8472, The Doctor was able to treat him with modified Borg nanoprobes to kill of the 8472 cells in Kim's body. The Borg later discovered this technique and worked together with Voyager to drive Species 8472 from the Delta Quadrant with modified nanoprobes incorporated into torpedoes. (ST: Voyager: "Scorpion, Part II")