The Sharingan is a Kekkei Genkai only known to the Uchiha Clan. It is a bloodline trate passed down the generations of Uchiha Clan members.

No other shinobi can know or learn it other than having a transplant like Kakashi Hatake did, other than that there is no exceptions. The Sharingan, unlike the Byakugan, is not

automatically activated in the user by birth. It is only first unlocked under some stressful or emotional condition, after which, though, 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 it gaining more tomoe, up to a maximum of three. As the Sharingan evolves, the user gains heightened abilities. The only level up

from the three tomoe Sharingan is the Mangekyo Sharingan, which is gained by the emotional stress stemming from the loss of someone close to the user. The Sharingan's first

and most well-known ability is that it grants the user the ability to memorize any technique that he or she witnesses, apart from other Kekkei Genkai techniques. The user can

memorize ninjutsu, genjutsu, and taijutsu with perfect accuracy, allowing the user to use the techniques as his own, or even modify them to create his own new techniques,

much like Sasuke Uchiha's Lion Combo. In order to reproduce a copied jutsu, however, one must have the necessary skill or ability to perform them. A prime example is Rock

Lee's brand of taijutsu. While Sasuke was able to copy some of Lee's moves, they put a much more significant strain on him since he hasn't trained nearly as much as Lee has.

In addition to physical skill and kekkei genkai techniques, the Sharingan cannot reproduce jutsu dependent on other factors, such as summons that the user has not signed a

contract with.