Nanotechnology is the manipulation of matter on an atomic and molecular scale. They usually took the form of microscopic robots, often referred to as nanobots or microbots. Many species had developed nanotechnology.
By humans
In 2009, Genetec Systems created nanoforms. Androvax planned to use them to build a spaceship and then destroy Earth, but was defeated by Sarah Jane Smith and her gang. (TV: Prisoner of the Judoon)
In 24th century Prague, nanoprobes were used to create everything from cars to houses. (PROSE: Nanomorphosis)
The Travellers used nanotech in some of their bonding ceremonies. (PROSE: Happy Endings)
In 200,000, nano-termites were used as part of the Vomit-O-Matic. (TV: The Long Game)
The Vardy were a type of microbot used on a human colony planet. (TV: Smile)
By other species
The Tzun created nanites which could separate the DNA of a living hybrid organism. (PROSE: First Frontier)
The Chula created nanogenes to heal their soldiers during wartime. (TV: The Empty Child/The Doctor Dances)
The people of Avalon created nanotech which was mistaken for magic by human colonists. (PROSE: The Sorcerer's Apprentice)
The Farrians used teleport disks that incorporated nanotechnology. (AUDIO: The Invasion of E-Space)
Selachians created nanites which could repair their battlesuits. (PROSE: The Final Sanction)
The Daleks created the Contagium, which could infect biological hosts with nanites, allowing the Daleks to control their minds. (COMIC: Fire and Brimstone) They later created nanoclouds which converted humans into Dalek puppets. (TV: Asylum of the Daleks)
The natives of Bellania II created nanotech which survived the collapse of their civilisation and the destruction of all life on the planet. (PROSE: Beltempest)
The quantum transducer used nanotechnology. (TV: Ghost Machine)
The Actilliasauraitius Mining Corporation used nanobots to set up a mine on the planet Adamantine. The Thirteenth Doctor later reprogrammed the nanobots to seal up the mine, thereby saving the rock people living inside the planet from destruction. (PROSE: Molten Heart)