Sharingan

Description
The Sharingan (写輪眼, Literally meaning: Copy Wheel Eye, Meaning (Viz): Mirror Wheel Eye) is the dōjutsu kekkei genkai of the Uchiha clan that appears selectively among its members.

It manifests as red eyes containing a single tomoe initially, yet this grows to two tomoe and eventually three after training. At three tomoe the Sharingan is said to have fully matured.

The way that the Sharingan is obtained is when an Uchiha feels an extreme emotion, which releases a special kind of chakra that affects the optic nerves, which then creates the Sharingan.

This Dojutsu allows the user to see chakra, gives increased perception which allows one to imitate pencil movements, read lips, and even copy hand seals and other things of the like. It also allows the user to copy almost any Jutsu they see (except for Jutsu from kekkai Genkai). The Sharingan also allows the user to emit Genjutsu, which has the ability to control the Tailed Beasts which has been done in a few cases like when Madara Uchiha used it to fight with Hashirama Senju.

There is also an evolved version of the Sharingan, called the Mangekyou Sharingan (万華鏡写輪眼, Literally meaning: Kaleidoscope Copy Wheel Eye). It is obtained when an Uchiha witnesses the death of a loved one or kills a loved one.