Nanites are microscopic machines and a form of nanotechnology.
In 2366, Wesley Crusher accidentally created sentient nanites that started to interfere with the USS Enterprise-D's operations. They were transferred to an uninhabited Kavis Alpha IV to form their own civilization. (TNG: "Evolution")
Sometime in the 2370s, a nanite infestation forced repairs on a holodeck program that enacted these modifications in it: the villain was no longer Prince Kael'thas Sunstrider but Praetor Kael, mages could wield spears, shamans could wield bows and rogues could have all the healing spells at their disposal, all of which fight in the holographic representation of the Senate Hall rather than in Magisters' Terrace, which was heavily reminiscent of Kevratas architecture. (RIS Bouteina)
In 2388, Captain Cell visited Kavis Alpha IV to acquire the nanites' help in stopping Lore and his Mudd androids from attacking the Federation. In the end, they succeeded in their efforts and permanently altered Lore so that he could not gain control of Mudd androids ever again. (Star Trek: Phoenix-X: "Cybernetic Showdown")