Nanofactured Robotic Devices' [NRDs or simply nanobots], designed using nanotechnology and capable of applying nanotechnology themselves: they can multiply and create improved offspring. Their future actions and descendants are stored into computer memory like digital genes. In the early 21th century, nanobots were only computer models, but a lot of things were learned. Nano-technology wasn't mature yet and the computer was the only way to see the process at work. That didn't stop researchers and with the help of molecular biologists a model was created. The researchers called themselves technical geneticists working on a predetermined technical evolution. When finally real nanofacturing was developed it didn't take much time before the first nanobots were 'born'. Nanobot techonology caused a breakthrough in space colonization when 100 nanobots were sent to the Asteroid Belt.

To the Asteroid Belt
A significant quantity of P-nanobots [the P from parent or pioneer] were fired in the direction of the Asteroid Belt. There are 5 types of P-nanobots. The first are the digbots, they dig, drill and cut in asteroids. The excavated material is being transported by transportbots to conversionbots who convert the materials into blocks of pure element. The conversionbots are connected with buildingbots who make parts. The parts are passed on to the assemblebots who first of all build a factory system around themselves, around the conversionbots and around the buildingbots. This factory interconnects a large number of these last 3 types of bots. They form a stationary fabrication unit. This unit will now build many digbots, speeding up the asteroid consumption. Also reserve parts and fuel are being created. The factory is programmed to stay building bots until the asteroid is consumed, maintaining a buildratio by means of feedback. After the asteroid is consumed the factory just hangs in space with the dig and transportbots attached to it. These last two have thrusting rockets and they use them to transport the whole unit to a new asteroid. Here the story starts over, only faster. This cycle goes on for some time until enough raw material is gathered. The raw material is used to create 20 km in diameter spheres with a complex of home units, workspaces, docking stations and other infrastructure inside. These are the so called City Asteroids. Not all the factoryunits start building this complex, some only create blocks of elements. These elements are stored for later transportation where needed [to Earth, the Moon, Mars, etc.].

The Web
The City Asteroids are connected to eachother by carbonfiber forming a web which keeps the asteroid system in balance. This web is Astropolis, the largest city in the Solar System.

The human contribution
In the meantime on Earth spaceships embarked with pioneer colonists, tough people who will make the complex livable. After them more colonists arrived and finally a whole society was formed.

The main criteria for a nanobot community
1. A particular quantity of nanobots per asteroid.
2. 5 types of P-nanobots.
3. A process to get pure elements from minerals.
4. Simple P-nanobots with simple applied nanotechnology build and assemble simple Fx-nanobots [next generations].
5. One buildingbot builds a part of a new nanobot and a factory builds the complete nanobot.

After this initial success more nanobots were designed. Because of their exponential growth from just a small quantity, they were sent to Venus and some moons of the outer gas giants, to start the process of terraforming. There they turned themselves into terraforming factories. This sort of terraforming is called Remote Automated Terraforming [RAT], and indeed like a rat it spread across our solarsystem. Not bringing the plague but life itself. Mars however was spared, terraforming was agreed to start when the Mars Science Institute had finished her areological research.