Nanite

Nanites, also called Nanobots, are very tiny robots that can be programmed to do work at molecular levels. They are usually very simple and can only be used for one task at a time.

Fiction

Beast Wars

Nanites, a tiny machine cluster far smaller than a cell, are the fundamental component of a Protoform. It is also the source of mutation phenomenon, such as Transmetalization.

Animated cartoon

Sumdac Systems developed a form of nanite that could dissolve organic waste, but after a mutation created by the AllSpark Key, they began to break down any and all matter they came in contact with. They were stopped by Wreck-Gar, who was seemingly destroyed in the process (though he did survive). Garbage In, Garbage Out

Rescue Bots cartoon

Plot details for Cody on Patrol follow. Spoilers have expired, you may remove this tag

Doc Greene has a container of nanites in his possession, but they have not been inventoried. Cody Burns stole these nanites to enhance his go-kart, Rolling Thunder. After the go-kart's brakes proved to be faulty, Rolling Thunder was diverted into Griffin Rock's junkyard, where the nanites then left the go-kart on their own power and entered the intake of the Scrapmaster, making it unable to distinguish between junk and being. The out-of-control garbage disposal was stopped when Heatwave cut its fuel tank, causing the nanites to enter into Boulder, taking control of his body. Bolder managed to get enough control of himself to drive the nanites into the power plant at Cody's suggestion, noting that the Nanites kept getting attracted to more powerful machines. The nanites then entered the plant's generators, eventually getting overwhelmed by the raw power, as planned. Cody on Patrol