About the 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.

Stages
When the Sharingan is first activated by a user, it has a different number of tomoe around a central pupil, varing among the users.[1][2] The wielder of the Sharingan, through continued use, evolves the Sharingan which involves gaining tomoe. The maximum number of tomoe in a conventional Sharingan is three. When the user gets three tomoe in each, he becomes able to predict all movement from his opponent, although he might not be able to keep up with him. The only level up from there is the Mangekyo Sharingan, which is said to be gained by the loss of a cruetial person or thing or people in your life.

The retina is a sheet of receptors at the back of the eye and is made up from two types of photoreceptor cells; rods and cones. Rods detect light levels, which means they only pick up black and white images. In humans, these are more common near the edge of the eye. Now, there is only a limited number of space for rods and cones in the retina, so if you increase the count of one you have to decrease the count of the other.

Essentially, you must trade color perception for more detailed perception in black and white, which is largely what enables us to perceive motion.

To put it more simply, rods detect motion and cones detect color.

Okay, now since you can’t really increase the sensitivity of a rod, you would have to increase the number of them. One way is to severely decrease the number of cones. Well, this won’t work without sacrificing color, and Uchiha’s don’t seem to be colorblind typically, so that must not be it. Another way is to make the retina bigger. But to get to the level of the sharingan by using this method your eyes would have to be huge!

Now, the obvious factor that sets Sharingan apart from normal eyes are the extra pupils, isn’t it? But how would that help? Well, if rods are more common around the edge of the eye, increasing the amount of pupils would increase the number outer edges to be lined with rods.

So, if the center pupil were devoted entirely to cones to retain a sense of color, then the space in the other pupils would be specifically for rods in order to get a better perception of motion, which is what the Sharingan is.

Now, the application of chakra to activate Sharingan could also be used to stimulate the portion of the brain used for memory retention, inspiring the user’s memory to become eidetic in nature during the activation of Sharingan, and thus giving them not only exceptional perception, but also the photographic memory required to be able to instantly recall any abilities seen.

But, this is the purely scientific view, which gives us no insight into the subliminal messages, so I also have an easier explanation.



A: Ability to see color.
1: Motion perception.
2: Copies all motion perceived.
3: Prediction motion- inferring through rational physics the action about to take place.
B: Ties pupils together for the ability to understand what one sees without getting confused. Without it, you would have three different eyes looking in three different directions and no idea what to focus on or what’s going on.

Abilities
The Sharingan's first and most well known ability is to memorize any technique that it witnesses. It can memorize Ninjutsu, Genjutsu, and Taijutsu with perfect accuracy, allowing the user to use the techniques as his own. In order to reproduce 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 physically nearly as hard as Lee has. In addition to physical skill, the Sharingan cannot allow the user to reproduce other Kekkei Genkai since the Sharingan user doesn't possess the same genetic trait. Additionally, Sharingan users cannot summon a creature which they have not made a contract with.

The Sharingan also grants the user incredible clarity of perception, allowing them to track fast-moving objects with ease and even predict the subsequent movements of those objects. The ability to track and predict movement is largely based on individual skill, as unskilled users have much more trouble tracking fast-moving objects. A fully-evolved Sharingan eye can track all but the quickest opponents, even if the user can't move at the same speed, (so even if the user can follow his or her opponents movements it doesn't necessarily mean their body will be able to react fast enough even though they saw the attack coming). This perception is also great enough to see through Genjutsu, depending upon the skill of the user, and the ability to observe the movement and flow of chakra, but not to the same extent or clarity as the Byakugan. Another ability of the Sharingan is the ability to see chakra as color, even through other objects. For example when Sasuke fights Deidara, he can see Deidara's bombs hidden under ground because of their chakra. Additionally, the Sharingan grants the user exceptional analytical powers, allowing them to instinctively pick up on various visual clues with little difficulty. In one instance, Kakashi had to shut his eyes to avoid accidentally reading Naruto's lip movements while he was spoiling the ending of one of Kakashi's Icha Icha books. Sasuke was also able to reproduce answers on another person's test by watching their pencil movements during the Chunin Exam.

The Sharingan also is capable of a unique brand of hypnosis that involves suggesting actions and thoughts to the opponent through simple eye contact. When used in conjunction with the other aspects of the Sharingan, this allows the user to perfectly mimic every move their opponent makes, even before they do, making it appear as if the user can see the future. More advanced Sharingan users can take the hypnosis ability even further by tricking or even trapping their opponent within an illusion. The potency of the Sharingan's illusion is dependent on the user's knowledge and skill with implementing Genjutsu.

Receiving the Sharingan
Unlike the Byakugan, the Sharingan does not automatically appear from birth in a user; instead, the user has to awaken it . After this first appearance, the user can then call up the Sharingan any time he or she pleases. Due to its unique nature, however, Kakashi's Sharingan cannot be deactivated, and thus he usually covers it to conserve chakra. The power of the Sharingan is judged through the number of tomoe in the eye, known as the "tomoe seal". It is not unheard of for a Sharingan user to have different numbers of tomoe in each eye. For example, Sasuke's Sharingan initially had two tomoe in one eye and one in the other. Upon his first regular activation of it, it had evolved to two tomoe in each eye. He evolved it to three in each eye during his battle with Naruto at the Valley of the End. A fully-matured Sharingan has three tomoe in each eye.

Transplanting Sharingan
It is possible to transplant Sharingan eyes from one person to another, as occurred with Kakashi and his deceased comrade Obito Uchiha. However, transplanted eyes do not work as well in a non-Uchiha body, causing more strain on the user, as is the case with Kakashi (extended use of his Sharingan will cause him to collapse). Uchiha clan members are not burdened with this weakness; while activation of the Sharingan does consume chakra, the drain is so small as to be insignificant. Itachi in particular seems to have no trouble keeping his Sharingan activated near-constantly.

Transplanting the Sharingan eyes from a living or deceased Uchiha is the only way to avoid the loss of sight over time from the Mangekyo Sharingan.

Mangekyou
The Mangekyo Sharingan (万華鏡写輪眼, Mangekyō Sharingan; Literally meaning "Kaleidoscope Copy Wheel Eye") is a heightened form of Sharingan. The Mangekyo Sharingan is distinguished from a normal Sharingan through its appearance, which changes the form of the tomoe seal. The appearance differs from user to user; Kakashi's and Itachi's both resemble pinwheels, Madara's and his brother's more look like more detailed forms of the basic three-tomoe Sharingan, and Sasuke's looks like a star. Those who have the potential to obtain it must make a great sacrifice in order to obtain it – according to Itachi, they must kill their closest friend. Itachi, Madara, and Izuna apparently do this to obtain the original version, but this is apparently not the only way to unlock it, as Kakashi has noted that everyone he cared about had died long before the start of the series, so how he developed his own variant is unknown. And even though Sasuke didn't kill Itachi, the trauma of losing Itachi (someone close to him) allowed him to unlock his own version. This means that the real way to unlock the Mangekyo Sharingan would be to lose someone close to you, but since Kakashi noted everyone close to him to be dead, it's still unknown how he unlocked his Mangekyo Sharingan. Also, the Mangekyo Sharingan can be transferred from person to person, as in the case with Sasuke, who got Itachi's Mangeyko Sharingan. The major drawback of the Mangekyo Sharingan is that it slowly begins to destroy the user's eyesight until they become completely blind and permanently lose their Sharingan. The only way to keep your eyesight is to steal the eyes of a sibling, combining the two Sharingan to create the Eternal Mangekyo Sharingan (永遠の万華鏡写輪眼, Eien no Mangekyō Sharingan), which prevents blindness.

In the long history of the Uchiha clan, only a few have been able to obtain the Mangekyo Sharingan-- Madara and Izuna Uchiha being the first. At present, there are three people alive who can use the Mangekyo Sharingan: Kakashi, Madara, and Sasuke.

The Mangekyo Sharingan gives a user access to the most powerful and forbidden techniques of the Uchiha Clan. Itachi has demonstrated though his Mangekyo Sharingan mastery over Amaterasu, Susanoo, and Tsukuyomi. Kakashi has used his Mangekyo Sharingan to perform Kamui. Sasuke's Mangeyko Sharingan hasn't displayed any unique abilities aside from Amaterasu. It is implied that with enough training, one can master all of the Mangekyo techniques as Madara did.



Itachi's Mangekyou
Itachi Uchiha gained the Mangekyo Sharingan by killing his best friend, Shisui Uchiha. With the Mangekyo Sharingan, Itachi is able to use at least three of the most powerful jutsu of the Uchiha clan. The first is Tsukuyomi, a powerful Genjutsu. This technique comes out of and puts strain on the left eye. Upon making eye contact with an opponent, Itachi can use Tsukuyomi to transport them to an illusionary world where days amount to a mere moment in reality. Because Itachi is in total control of this world, he can torture an opponent in any way imaginable, leaving them crippled and in a state of mental collapse, though he hasn't gone further than 3 days. The second technique is Amaterasu. This technique puts strain on the right eye, and caused his eye to bleed during his final fight with Sasuke. Described by Zetsu as the ultimate ninjutsu, it is shown to be capable of burning through almost anything by creating a jet-black flame said to be as hot as the sun and capable of burning for seven days and seven nights.

The last of these techniques is the devastating Susanoo. The technique summons a massive ethereal warrior, which then fights on behalf of Itachi. In the left hand, the warrior wields Yata's Mirror (八咫鏡, Yata no Kagami; Literally meaning "Eight Span Mirror"), a shield that's capable of reflecting several attacks, and in its right, the legendary Sword of Totsuka (十拳剣, Totsuka no Tsurugi; Literally meaning "The Sword Ten Hands Long"), also known as the Sakenagi Longsword (酒刈太刀, Sakenagi Tachi; Literally meaning "Sake Cutter Longsword"). The Sword of Totsuka, commonly sheathed in a sake jar held by a third hand growing from Susanoo's right forearm, is an ethereal weapon with an enchanted blade capable of sealing anything it pierces in an alternate dimension where they're trapped in an eternal dream-like illusion.

All of these techniques, however, use massive amounts of chakra and also cause ever increasing damage to the user's eyesight. Itachi himself becomes exhausted if using Amaterasu and Tsukuyomi both consecutively and has to deactivate his Sharingan. Soon he claims that his ulterior motive is to steal Sasuke's eyes to awaken his own Eternal Mangekyo Sharingan. During the fight with Itachi and Sasuke, Zetsu has revealed that the "Left Mangekyo" possesses the Tsukuyomi and the "Right Mangekyo" holds Amaterasu. It is unknown where Susanoo comes from, and if Itachi even needs the Mangekyo Sharingan to make it work, although it is known that he needs to have at least awakened it to use it.

Although in Itachi's final fight the Mangekyo Sharingan techniques seemed to cause the respective eyes to bleed, this was never before seen to happen when the techniques were used. This may in some way be caused by Itachi's apparent weakness during this battle, or simply due to his usage of his Mangekyo over time.


Kakashi's Mangekyou
Kakashi Hatake developed his own version of the Mangekyo Sharingan during the timeskip. Kakashi mastered a technique that creates a localized interdimensional space-time ninjutsu called Kamui, allowing him to target any object and send it to another dimension. The attack requires considerable effort to aim precisely and appears to leave Kakashi's chakra significantly drained; he collapses after using the technique three times even at full strength in a single day (compared to his other original move, Lightning Blade, which he can use four times a day in part I of the series while he appears to be able to use it six times or more a day-as shown in his battle against Kakuzu).

The appearance of the pupil and tomoe in Kakashi's Mangekyo Sharingan differ from that of Itachi's; Kakashi's looks more like a pin-wheel. Before this was shown, it was thought that one had to kill their best friend to acquire the Mangekyo Sharingan, yet this has been dissproven in both Kakashi and Sasuke, as Sasuke did not kill Naruto, but rather the traumatic effect of losing Itachi after discovering he was really trying to protect him caused his Mangekyo Sharingan to activate, while Kakashi states that everyone he cared for was already dead, and had been for years and he had not activated his Mangekyo Sharingan. Currently the cause of his Mangekyo's activation is unknown. Although it can be assumed that Kakashi was overcome with emotion that he ended up activating the Sharingan like Sasuke.


Madara's Mangekyou
Madara Uchiha was actually the first person to wield this dangerous weapon. When he was young, he and his younger brother were the first people to gain the Mangekyo Sharingan. It took the form of a ring with three circular holes in it. He eventually grew blind from overusing it.

ETERNAL MANGEKYOU SHARINGAN
After he killed Izuna Uchiha and pried his eyes out (though Madara claims the eyes were a sacrifice from his brother for the good of the clan), this unlocked the "Eternal" Mangekyo Sharingan. His Eternal Mangekyo Sharingan in appearance looks identical to Madara's first Mangekyo combined with Izuna's Mangekyo.

It is believed Madara used its power to control the Nine-Tailed Demon Fox and sent it to attack Konoha on one occasion, though he denies this. Regardless, the attack failed because of the Fourth Hokage's sacrifice.

With the Eternal Mangekyo Sharingan, Madara mastered all the secrets and techniques of the Mangekyo Sharingan. Also, according to Itachi, Madara unlocked a final and ultimate eye technique, which was the reason why Itachi spared his younger brother Sasuke - in the hope of taking Sasuke's eyes to achieve the Eternal Mangekyo Sharingan and gaining the ultimate Mangeyko Sharingan technique. Currently, the only technique that Madara has shown is an unnamed space/time ninjutsu, which makes him nearly invulnerable as most attacks will pass through him.

Due to his claim that he will use the Tailed Beasts to return his eyes to their former glory, his Eternal Mangekyo Sharingan eyes might have become damaged.

Izuna's Mangekyou
Izuna Uchiha once possessed the Mangekyo Sharingan as well, his took the appearance of three bars stretching out of his pupil. It is said that he developed his around the time his brother Madara did.

Madara later pried these eyes out of his head (Madara claimed he gave them to him) thus creating Madara's Eternal Mangekyo, which took the appearance of Madara and Izuna's Mangekyo combined.


Sasuke's Mangekyou
After Sasuke Uchiha's battle with Itachi, he wakes up in a cave with Madara nearby. Madara removes his mask to reveal his Sharingan, which upon sight triggers the activation of Sasuke's Mangekyo Sharingan (in the form of Itachi's) and the Amaterasu, setting Madara ablaze. However Sasuke seems to have no control of this and quickly clamps his hands over his eyes.

Madara then explains that Itachi properly transferred all of his eye techniques to Sasuke, to protect his little brother, as a fail safe. It should be noted that during the time Sasuke's Mangekyo Sharingan first emerged it was actually Itachi's Mangekyo transferred to him. This Mangekyo Sharingan still required someone close to him to die. Therefore, Itachi, knowing he had a terminal illness, pushed Sasuke to the limit in battle. This allowed Orochimaru to emerge so that Itachi could purge his influence from Sasuke. Then, by dying before his brother's eyes, he could become Sasuke's "sacrifice".[1]

The first time Sasuke is shown with it is when he announces the formation of the new team "Hawk," to crush Konoha.[2] Sasuke's Mangekyo Sharingan takes the appearance of a six-sided star often resembling the atomic model, and unlike other Sharingans, which have a black design and red background, Sasuke's is the first one that is shown to have a red design and a black background. He has shown the ability to use a genjutsu which can "exploit fearful hearts", in this case to extract information from a victim. This genjutsu could possibly be the Tsukuyomi. [3] He can also use Amaterasu, this time against Kirābī, but with his own Mangekyo and with the opposite eye Itachi used it with.[4] He can also put out the Amaterasu flames[5] as seen with Kirābī and Karin when one of Kirābī's burning tentacles hit her.

Sasuke has been shown to suffer the same side effects as Itachi did when he evoked the powers of the Mangekyo Sharingan; strain and bleeding of the eye (though this might have been because Sasuke was in a weakened state at the time due to the injuries he sustained in his fight with Itachi), rapid draining of chakra, and slowly deteriorating eyesight.