We have learned that it is possible to transplant Sharingan eyes from one user to another, as is the case when Uchiha Obito (team-mate of a young Hatake Kakashi) gifted his eye to Kakashi upon his own death, the implant was performed by Rin (team-mate of Hatake Kakashi and Uchiha Obito). The drawback of being an un-natural user of the Sharingan is that it causes much more strain on the body of the user. The Mangekyou Sharingan (Kaleidoscope Copy Wheel Eye) The Mangekyou Sharingan, literally Kaleidoscope Copy Wheel Eye, is a higher form of the Uchiha clan Sharingan. Until recently, it was thought that only natural Sharingan users could obtain that technique, but it seems that Kakashi proved everyone wrong by activating the Mangekyou Sharingan to rip off one of Deidara's arms. The Mangekyou Sharingan is not easy to obtain however for those who are not made of cold blood as they must make a tremendous sacrifice in order to obtain it, they must kill their best friend. In Itachi's case, we learned that he killed Uchiha Shisui. As for Kakashi, his best friend, Uchiha Obito, sacrificed himself to save him, making Kakashi a potential Mangekyou Sharingan user. However, despite its immense destructive power, the Mangekyou Sharingan is a double edged sword. Hence, the Sharingan 'causes a terrible strain on the user's eyes and eventualy deteriorate his eyesight. Morevover, using the Mangekyou Sharingan uses enourmous amounts of Chakra. And for unatural users of the Sharingan, such as Hatake Kakashi, it's even worse. But, despite its drawbacks, the Mangekyou Sharingan is the deadliest technique known to this day. To date only three people out of a possible four people have obtained this legendary eye, Uchiha Itachi, Hatake Kakashi and an unknown Uchiha ancestor. The only other person who could possibly attain the Mangekyou Sharingan is Uchiha Sasuke, to obtain this he would have to kill his best friend, Uzumaki Naruto. With the Mangekyou Sharingan activated one major advantage is to be able to use the three most powerful jutsu possible, two of which have been revealed so far: Tsukuyomi and Amaterasu.