Nanomachine

Nanomachines are tiny microscopic machines which are injected into people's blood to distinguish that person for various uses. Some of these include:


 * Codec conversations, Nanomachines recognise specific frequencies and use them to contact certain people.
 * In MGS2, in order for Solidus Snake to launch Arsenal Gear, he has to allow President Johnson to enter in the special code into the Black Box of his own free will. They are able to detect this by his Nanomachines transmitting various signals to the Black Box, such as Heartbeat, Brain Waves, etc.
 * Storing information, a.k.a. Solidus tells Raiden in MGS2 that his Nanomachines are carrying information on who The Patriots really are.