Inhibitor chip

Inhibitor chips were biochips that were engineered into the Kaminoan clone troopers of the Grand Army of the Republic.

Description
The chips were surgically implanted into the brains of every single clone embryo past stage three of development. Nominally supposed to prevent clones from being overly independent and aggressive, their true function was initially intended by Sifo-Dyas as a built-in safeguard against control by rogue Jedi or Sith. However, Dooku's covert involvement in the cloning program  ensured that from the very beginning of the Clone War, the chips would serve an integral part of the Sith conspiracy to control the clones and guarantee them capable of killing their Jedi Generals in accordance to Order 66.

History
Sifo-Dyas was the only Jedi to know of the chips existence. Upon his death, only the newly fallen Lord Tyranus, Sidious and such key Kaminoans as Nala Se who were involved from the beginning of the cloning program knew of the chip's true purpose, and they sought to repress any knowledge of it. The chips were subsequently supplied by Tyranus, whose involvement remained a closely guarded secret by the Kaminoan leadership. The Kaminoans themselves apparently believed Tyranus to be a secretive member of the Jedi Order, even though through his directives they actively kept the nature of the chips from being known by anyone else.

Around 20 BBY, the chip of the clone trooper Tup malfunctioned, causing his Jedi-killing protocol to activate prematurely. Another clone nicknamed "Fives" ended up discovering the truth about the inhibitor chip, but he was framed for attempting to assassinate Supreme Chancellor Palpatine and was shot by one of his fellow clones before he could reveal it.

It was only towards the end of the Clone War that the Jedi learned the elusive figure they had identified as Tyranus was in fact Count Dooku. This lead to the realization that the Sith had been involved in the cloning program from its inception, although they knew not to what purpose. They chose to keep this knowledge a secret from the Senate, as they thought it would destabilize the Republic and undermine the war effort. Instead, they resolved to take the only path they could see available, which was to play the game they now knew to have been orchestrated by the Sith, and bring an end to the war as quickly as possible.

Appearances

 * Star Wars Episode II: Attack of the Clones