Nanotechnology

Nanotechnology (often shortened to Nanotech) is a field of technology involving the manipulation of matter on extremely small scales. Humanity first began experimenting with nanotechnology around the turn of the 21st century, and the UNSC currently makes use of nanotech for a variety of purposes.

History
The term "nanotechnology" was coined by the Japanese scientist Norio Taniguchi in 1974.

Example usage
The following are example applications of nanotechnology, used by various groups.

UNSC
The UNSC utilizes nanomachines for several purposes, most notably in conjunction with MJOLNIR armor systems. As of 2552, the UNSC had developed nanotechnology designed to perform repairs on MJOLNIR armor while its Spartan occupant rested in cryo-sleep. Given enough time and in the hands of a capable "smart" AI, these nanomachines were capable of completely overhauling a suit. The Charon-class light frigate Forward Unto Dawn carried a supply of nanomachines for this purpose, which the AI Cortana used to upgrade and re-design John-117's MJOLNIR Mk. VI while the Dawn drifted through space for four years.

A similar form of nanotechnology was incorporated into the MJOLNIR Mk. VII, allowing the suit to repair and upgrade itself autonomously during cryo-sleep. This feature was presumably carried over to the MJOLNIR [GEN2].

Forerunner
While no singular examples of Forerunner nanotechnology are known to exist, their level of technological advancement would imply that at least some of their technology involved a form of nanotech.