Sharingan

The Sharingan (写輪眼; Literally meaning "Copy Wheel Eye", Meaning (Viz) "Mirror Wheel Eye") is a Kekkei Genkai, which appears in some members of the Uchiha clan of Konohagakure. Some think that it was derived from the Byakugan many years ago. It allows the user to comprehend the attack of an opponent almost before the attacker knows what attack they are making. The Sharingan also allows the user to see the flow of chakra within a person, but to a lesser extent than the Byakugan.