Self-Replication

Something is said to be self-replicating when it can make a copy of itself given the necessary materials. This occurs in a very complex form in biology where, for example, DNA self-replicates given the proper chemicals and catalysts and self-bacteria replicates given the proper nutrients. However, self-replication of artificial machines has thus far been very limited; most research has focused on self-replication in a virtual environment while work on physical mechanisms has only resulted in being able to assemble a few parts. This is nowhere near the scale envisioned by science fiction writers where nano-machines can create copies of themselves using raw materials and then coalesce into a fearsome creature.