Nanos are extremely tiny machines that can assemble themselves and can self-replicate, allowing them to be programmed to do practically anything.
In the Uglies series, nanos are an omnipresent part of everyday life.
- The Hole in the Wall: Pretties are allowed to get whatever they want, such as toys and clothes, by using a hole in the wall. As a self-contained nano factory, it functions similarly to a 3D printer. They can turn "nano-frames" into usable objects by weaving nanos together. When the Pretties get tired of anything, they can just toss it back into the recycler, which breaks it back down into raw material. Anyone can make and share designs for the hole in the wall. In Yokohama, when anyone "prints" something someone has designed, that person's face rank goes up.
- The Cure: Maddy's first cure uses nanos to devour the lesions in Pretties' brains. Later, she used her observations of Tally to create a cure that works faster and more safely. She also made a cure for Specials, which most likely work in a similar fashion. She mentions that the cure for cancer uses nanos to "eat" the cancer away.
- Hunger Nanos: These silvery-colored nanos are designed to be used as a weapon. They are programmed to re-create themselves by consuming anything they touch except for the beaker they're stored in, a black "antidote" foam, and plain old dirt (in case they got out of control and tried to eat the whole world). Shay and Tally encounter them in their city's armory and use them to escape, destroying the entire building in the process.
- Smart Matter: An invention that resulted from the mind-rain, smart matter are general-purpose nanos that can be programmed to mimic any substance. At least in Yokohama, they have been widely used in architecture as building supports, allowing the buildings to hover and periodically change their shapes.
- Nano-Glue: These nanos analyze whatever surface they come into contact with and then become the right sort of glue to stick to it.
- Dental Nanos: Pretty teeth are made out of an unbreakable substance unless special dental nanos are used to soften them.
- Fertilizing Nanos: In the Smoke, these nanos are used in the latrines to break down sewage into fertilizer.
- Repair Nanos: Specials store these nanos in their bodies so that their muscles and tissues heal very quickly when damaged. They generate substantial amounts of heat when they're at work, showing up as white-hot in infrared.
- Operation Nanos: These nanos are used within operating fluid in surgical tanks to keep the patient's tissues alive.