Nanites are microscopic robots created by Doctor Eggman during Sonic the Hedgehog's absence from Mobius. Programmed or controlled by an AI, they can restructure themselves into various forms and are thus extremely versatile.
Taken control of by A.D.A.M., they became a serious menace to several groups of Freedom Fighters. A.D.A.M. spread them out and formed a city-like structure with them, eventually building a giant spire with which he planned to collect all the Chaos Emeralds in the universe by jump-starting the Great Harmony through the use of Turbo Tails and Super Shadow. Using nanites infected in the robotic components of Nicole, Bunnie Rabbot, and Jules Hedgehog, as well as the inorganic shell of Tommy Turtle, he used them all as tools in his plan; however, when he was ultimately destroyed, Nicole took control of the nanites, reshaping the nanite city into a recreation of the former Mobotropolis for her friends.