- You may also be looking for Nanoprobe (PNR episode).
Nanoprobes is a form of nanotechnology used by the Borg to assimilate others into the Collective. They are injected into the bloodstreams of victims they are quickly able to gain control of the victim's cellular functions. (VOY: "Scorpion")
Given the inherent self-replicating nature of nanoprobes, they could also be used to build new pieces of technology or even space vessels. One such ship was observed in 2385, grown after its six inhabitants disconnected from their Collective. (Star Trek: Abandoned: "Solitude")