Bionano wetware that goes in and out of fashion across the Nexus, but is especially popular among biont sapients of the Fiarro Twinworlds (Argelander Sector, NoCoZo), Nova Terra, and elsewhere.
Smart pharmaceuticals and virus-sized bionanites are applied by dermpatches, cosmetics, ingested, or inhaled. Once inside the body they make their way to the centres of the brain that control behaviour and sense of personal identity.
The encoded persona is then absorbed into the psyche, causing temporary or permanent personality modification (depending on how the treatment was programmed and its potency). Occasionally the wetware is incompatible with the user's psychological profile and psychosis may result; sometimes this psychosis is in fact the desired outcome.
Although Other Self is widely used throughout the civilized galaxy, the bionts of the Fiarro Twinworlds have made its application into a real art.