The Sharingan meaning "Copy Wheel Eye",is a dōjutsu kekkei genkai, which appears in members of the Uchiha clan. It is one of the three great dōjutsu, along with the Byakugan and the Rinnegan.
Stages
The Sharingan is not automatically activated in the user by birth. It is only first unlocked under some stressful or emotional condition after which the Sharingan may be used freely. When the Sharingan is first activated by a user, it has a different number of tomoe around the central pupil, varying between users. The wielder of the Sharingan, through continued use and training, evolves it further which involves gaining more tomoe, up to a maximum of three per eye. As the Sharingan develops, the user gains heightened abilities.
Abilities
The first of the Sharingan's powers is being able to see the flow of chakra. The Sharingan can tell if a person is under a genjutsu because the person's chakra flow would be irregular.
The Sharingan's second-most prominent ability grants the user an incredible clarity of perception, allowing them to easily recognize genjutsu and different forms of chakra, though not to the same extent as the Byakugan. This also allows the user to pick up on subtle details, enabling them to read lip movements or mimic something like pencil movements