Self-replicating systems

Self-replicating systems or Von Neumann machines are typically robotic or nanorobotic and reproduce by creating miniature copies of themselves which then grow larger over time. They may have rudimentary or more advanced artificial intelligence code to prevent self-destruction or shutdown from external sources. Systems like these can take over a planet, solar system or beyond, and this uncontrollable spread or swarm can lead to a technological singularity.

Goo
A nanoswarm capable of spreading and growing, particularly if it has escaped its original parameters and lost control, is commonly referred to as goo. These are molecular assemblers and their numbers may be many orders of magnitude more than nanobots. They tend to 'eat' or disassemble (black goo) all available material, ranging from elements like carbon (grey goo) to industrial components (khaki goo) to ecologies and biotics (green goo). They can become a nuisance or hazard, and in worst cases an uncontrollable infestation that starts with ecoregions, then the whole planet (ecophagy) then a singularity. If programmed correctly, a controlled goo can be used to clean up industrial disasters like oil spills, but it is critical to have a stopping point.

Von Neumann probe
A von Neumann probe is a spacecraft capable of replicating itself. It would consist of:
 * Probe: which would contain probing instruments and AI to guide the construct.
 * Life-support systems: mechanisms to repair and maintain the construct.
 * Factory: mechanisms to harvest resources and self-replicate.
 * Memory banks and Storage: store programs for all its components and information gained by the probe.
 * Engine: motor to move the probe.