Nanos

Nanos used to be one of the primary components of the leveling system in Sonic Battle Universe. Nanos are small, miniaturized versions of Sonic characters designed to aid the player through various means. There are currently 36 usable Nanos in the game. Although the NPCs of characters in the game have more realistic looks, the Nanos of them still retain some of their original cartoony appearance.

History
Nanos were created by the unlikely team of Sonic and Eggman. When Dark came to Earth and began his invasion of the planet with his horde of Darkness Monsters and DarkBombs, Tails and Eggman began to develop the best way to fight against the invaders. The result of this development were Nanos. By harnessing the essence of Planet Darkness and its monsters, Dark Matter, they could create the Nanos, the ultimate weapon against Dark and his minions.

In the story, the Nanos were originally created in The Past, but unfortunately, it seemed like they were created a little too late, and the people in The Past could only slow down the infection of the world. But when the player arrived in The Past, due to Sonic's time travel experiment, Past Sonic came up with a new plan for the Nanos: Sending the instructions for how to create Nanos back to their Future selves, with the player, they could get the right tools to fight Dark at the right time, and thereby prevent the dark past. Thanks to the help from the player, the remaining heroes managed to send the instructions to create Nanos, back to the past, and their past selves managed to mass produce the Nanos. It is also hinted that the Great Machine was built after the player sent Sonic a message via a wormhole from The Past.