Nanomites were planted inside beings and technology. It allowed weapons to upgrade and health to be enhanced in the form of nanotech. To obtain an enemy's Nanomites, had to be killed. The stronger the enemy, the more Nanomites it had.
Nanomites were first introduced with Megacorp. Megacorp's armor and weapons were both able to absorb Nanomites. Once the armor absorbed enough Nanomites, the maximum Nanotech of the user increased. When enough is absorbed by a weapon, it upgrades, becoming more powerful. After introduced by Megacorp, others like Gadgetron decided to make their technology Nanomite-absorbent.