Nanotechology covers the use of submicroscopic machines to do many different things.
Sometime in the 13th century, an unknown race provided nanotechnology to the inhabitants of the Ilaiyen Archipelago on planet Sigma Niobe II, which kept them free from disease and allowed them to quickly recover from even fatal injuries. These abilities became the stuff of legends around the globe, and even on other worlds.
By the mid 22nd century, the Denobulans were known to have experimented in creating examples of nanotechnology. This form of research was recalled by a United Earth researcher at Arctic One in 2153.
The enigmatic Grigari species were known to had made extensive use of nanotechnology which was the secret of their medical technology. They made use of molecular assembly machines that were capable of expertly weaving together both steel and fleshing; uniting the living nervous system to link directly with the computer control circuits. They used this type of technology to save the life of Adrik Thorsen and extend his life span.
By the middle of the 24th century, research into this field of science was conducted by both the Federation and the Romulan Star Empire, though neither were successful in producing effective examples for active use.
A powerful Gamma Quadrant race had developed advanced nanotechnology centuries before 2369. They imprisoned the Ennis and the Nol-Ennis, two of their factions, on a moon and deployed nanoprobe-like devices which would resurrect those who had been killed in an eternal war.
In 2369, Doctor Julian Bashir found similarities between nanites and the artificial microbes that resurrected the Ennis and the Nol-Ennis. A countermeasure against the nanotechnology had been found by 2376.
In 2369, Elias Vaughn and Ruriko Tenmei used trillions of nanites to find and un-write the code of Cren Veruda's artificial intelligence, which the Borg had found at Uridi'si.
In 2370, during the invasion of the Heran home world, the Klingon and Federation forces discovered their hand-held energy weapons to be useless due to the Heran use of nanites.
In 2372, the Doctor aboard USS Voyager was able to use nanites as a forensic tool to identify Frank Darwin's murderer as Lon Suder.
In 2376, Simon Tarses used medical nanites to treat injuries that Ro Laren suffered after Taran'atar's attack. They were able to limit the genetronic matrix's activity at the molecular level and prevented accidental metastasization.
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 off 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.
A Founder encountered by the crew of the USS Defiant in 2376 was able to destroy nanoprobes by shapeshifting and crushing them when they had been injected into her body.
In 2377 a group of Vulcans attempted to use nanoprobes to devise a cure for Bendii syndrome. Unfortunately they lost control and in the process created The Wardens, a group bent on Vulcan logic with a Borg like devotion to spreading their cause. The Wardens spread their influence to numerous nearby worlds, mass producing their modified nanoprobes to take control of billions of people. As the Wardens approached galactic domination a team from the USS Incursion was able to access their headquarters on Vulcan and reprogram the nanoprobe factories to produce nanoprobes with conflicting orders which cancelled out the effects of the Wardens and returned the galaxy's populace to normal.
In 2380, Cadet Torvig Bu-Kar-Nguv on board the USS Titan initiated a series of experiments on his crewmates including adjusting the replicators to infuse nanoprobes into the crew's food which would then attach to their intestinal walls. Torvig was hoping to test whether the expression "gut feelings" had any basis in fact.
In 2381, USS Titan Chief Engineer Xin Ra-Havreii designed upgrades to the vessel's holotank to allow Chief Science Officer Melora Pazlar to operate the system in a zero-g environment. Part of the control interface included a network of embedded nanosensors in a suit extending from the souls of her boots to a pair of form fitting gloves.
The Heran Modality deployed nanites all over their homeworld of Hera, which worked as a method of suppressing enemy ground weaponry. This worked by the nanites affecting the power linkages of the weapons, making them useless in a battle on the planet, thus forcing invaders to make use of simpler methods to combat the Heran defense forces.
Nanotechnology was an advanced form of molecular engineering involving the manufacturing, by molecular chemistry, of tiny machines smaller than living cells.
The applications of the technology were potentially limitless. In medicine, it could result in nanomachines capable of being injected into the bloodstream and traveling to specific areas of the body to begin repairing injuries or aid in the healing of diseased tissue. In structural engineering, it could result in building materials that could reassemble themselves on a molecular level.
Nanoprobes can also be modified for a variety of medical of technical tasks, and have also been modified for warfare.
Nanites are used by the Federation for medical purposes and were designed to work inside nucleii during cellular surgery. When they were not used, nanites were stored in a non-functional state. Sensors do not register nanites as being alive and when necessary nanites could be destroyed with a burst of high-level gamma radiation.
Many species have researched nanotechnology for various applications; the Denobulans were said to use advanced nanotech in medicine in the 22nd century.
Another known nanite-like device is the nanoprobe, used by the Borg for many purposes including the probing and assimilation of foreign species and technologies.
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.
The Borg Collective made use of nanites on their Diamond vessels as a method of disrupting enemy communication and computer systems. These nanites were injected into an enemy ship where they began to scramble the computer interface, causing chaos on the target vessels.
This served as a special ability among the Borg Diamond which, when used, caused the interface to move randomly across the screen making it difficult to issue commands to an infected unit.
In the mirror universe, the Obsidian Order developed a way to use nanites as passive recording devices, to spy by secretly recording conversations. The Order's research and development team developed a way to deploy them, using miniature particle ejectors containing programmable cylinders containing thousands of nanites. These nanites were capable of recording through tissue from inside the lungs or intestines of a living being with some being capable of clinging to a target's hair or clothes for a day or so. Once loaded into the ejector, it was a simple matter to implant the machine to the users lips. After which, a certain amount of pressure activated the nanites which blew towards the target and recording everything relating to them. They were capable of being remotely triggered at a later time and once they were retrieved, it was possible to gain an entire day's worth of conversations from the machines as they worked together for redundancy.
The head of the Order, Enabrain Tain, planned on using this technology on Gul Skrain Dukat in order to learn his secrets so that Tain could destroy his career. At the time, Tain did not share any of the secrets of the technology within the rest of the Klingon-Cardassian Alliance or even his own government.The short lived Borg-Romulan alliance made use of nanites that were not constructed from Borg technology to help regenerate the body of James Tiberius Kirk as a plot to use him against the Federation.