Sharingan (Copy Wheel Eye) is a technique unique to the Uchiha clan, characterized by a bright red eye with black tomoe (commas) surrounding the pupil. Sharingan gives the user the ability to analyze genjutsu (illusion techniques), taijutsu (martial arts techniques) and ninjutsu (ninja techniques) and counter-act them. It also gives the ability to copy the movements needed to complete virtually any technique. Sharingan only activates later in life, during times of severe emotional stress. The appearance changes over time.
Two-tomoe Sharingan are capable of piercing genjutsu. It also allows the observation of chakra energy in other ninjas and can be used to determine if someone is trapped in a genjutsu. It also can distinguish real opponents from clone illusions.
Three-tomoe Sharingan have the abilities of a two-tomoe Sharingan. Additionally, they can predict an opponent's next move based on muscle tension, allowing the user to strike and hit their opponent ahead of time. Three-tomoe Sharingan also can create a genjutsu or hypnosis upon eye contact, or to reflect a genjutsu.
Mangekyō Sharingan (Kaleidoscope Copy Wheel Eye) is a legendary technique that very few Uchiha attain. It bestows different abilities to each user. Attaining Mangekyō requires an Uchiha to murder their best friend. Overuse of Mangekyō causes gradual eyesight loss, which can only be remedied by transplanting the eyes of another Mangekyō user.
Itachi Uchiha's Mangekyō grants him the abilities Amaterasu (Goddess of the Sun), Tsukuyomi (God of the Mood) and Susanoo (God of the Sea and Storms). Amaterasu creates black flames that burn anything in the field of vision at the time of casting. These flames last seven days and nights. Tsukuyomi locks the target in an illusion that alters the perception of time and leaves the victim at Itachi's mercy. Finally, Susanoo creates ethereal flaming armor and a flaming sword and shield for Itachi, rendering him virtually invincible.
Sasuke develops the Mangekyō after battling Itachi. Sasuke's Mangekyō is similar to Itachi's. Sasuke can summon, and improve, Susanoo, and use Amaterasu and Tsukuyomi. Sasuke's Amaterasu is automatic, based on proximity to an enemy. Sasuke's Tsukuyomi is not as powerful or skillful as Itachi's. Sasuke's Mangekyō full power has yet to be displayed, and has a unique, flower-like appearance with inverse color patterns from other Sharingan.
Kakashi Hatake's Sharingan eye is a transplant from Obito Uchiha. Kakashi has managed to attain Mangekyō despite not being an Uchiha. Kakashi's version manipulates space and creates a crushing vortex, similar to a black hole. Absorbed matter is collapsed upon itself and sent to another dimension.
Madara Uchiha was the first Uchiha to awaken Mangekyō. The full extent of his powers has not been revealed, but his Mangekyō appears to have similar abilities to Kakashi's, allowing the manipulation of space to teleport objects, and phase different parts of Madara's body in and out of reality. He also has the ability to subdue the Nine-Tailed Demon Fox, a fearsome demonic entity with immeasurable power.