Three Great Dōjutsu

Dōjutsu (Literally meaning "Eye Techniques") are genetic ninja abilities that utilise the eyes, granting the wielder ocular abilities. Being a by-product of specific kekkei genkai, dōjutsu are not classified as one of the major jutsu types. They do not require the use of hand seals and in some cases facilitate in the use of or defence against genjutsu, taijutsu and ninjutsu and then defeat their opponent. All known dōjutsu also provide the user with some unique abilities, such as an extended field of vision or predictive capabilities. The use of dōjutsu often-time consumes a great deal of chakra. It should also be noted that along with the eye itself, techniques that stem from the eye's use are also known as dōjutsu. By transplanting the eye in question, it is possible for people to possess the dōjutsu, despite not being in the clan that the dōjutsu originates from.

Byakugan
The Byakugan (Literally meaning "White Eye") is the dōjutsu kekkei genkai of the Hyūga clan. Those who inherit the blood of this clan have almost featureless, white eyes. When the Byakugan is activated, the user's pupils become more distinct, and the veins near their temples bulge. It also appears that unlike the other two great dōjutsu, all members of the clan possess, and can use the kekkei genkai from birth, as opposed to needing to awaken or else, not inheriting it at all.

The Byakugan's abilities have left it highly coveted by the other villages, as evidenced by Kumogakure's attempt to steal it; an event which led up to what is known as the "Hyūga Affair". Ao of Kirigakure was able to obtain a single Byakugan from a Hyūga he defeated, and goes to great lengths to protect it.

The Hyūga clan's Main House, in order to reduce the probability of having their eyes fall into enemy hands, as well as to have the Branch House give absolute servitude to them, placed a cursed seal onto the foreheads of the branch house members, which would seal away their Byakugan forever upon death. Unlike a transplanted Sharingan, a transplanted Byakugan can be activated and deactivated at will.

The primary ability of the Byakugan gives the user a near 360º field of vision, except for one blind spot at the back of the neck above the first thoracic vertebra. Upon activation of the dōjutsu, the wielder is granted an automatic 50 metre field of vision around themselves which can then be extended at their discretion.

The second ability is being able to see through solid objects, as well as some degree of telescopic sight. It can also see through most barriers, and other things such as smokescreens, differentiate between non-corporeal clones and can see through techniques that would otherwise hide an opponent from normal sight. The distance and the degree of telescopic sight varies from person to person, and can be improved through training.

The third and one of the greatest uses of the Byakugan is the ability to see chakra, chakra flow, the chakra circulation system inside the body with great detail as well as the colour of chakra.Particularly skilled users of the Byakugan can take the Gentle Fist style one step further. Along the keirakurei are 361 pinprick-sized nodes called tenketsu, or chakra points, which only the more skilled users can see. When struck, the Byakugan user can choose to either seal, or forcibly open these tenketsu, thus giving the user complete control over their opponent's chakra system. So, with precision, all those points along the victim's body can be sealed, stopping the chakra flow to those areas. Constantly using the Byakugan over a very long period of time causes severe eye strain.

Weilders:

Rinnegan
The Rinnegan is reputed as the most exalted eyes amongst the Three Great Dōjutsu. It is characterised by its ripple-like pattern which spreads over the eyeballs, with light purple irides and sclerae.

It was admired as being able to bring forth all ninjutsu. It was said that in times when the world is in disorder, a person is sent down from the heavens to become either a "God of Creation" who will calm the world, or a "Destroyer" who will reduce everything to nothingness. The Rinnegan allows the user to use the Six Paths Technique.

The first person to possess the Rinnegan was the Sage of the Six Paths. Because of the Sage's mythical status, many people believed the Rinnegan was only a legend or a mutation. Because the Rinnegan was originally wielded by the Sage of the Six Paths, re-merging his bloodlines: that of the Senju and Uchiha can lead to that person awakening this dōjutsu.

One who gains the Rinnegan has access to a multitude of abilities. On its own, the Rinnegan allows the user to see chakra, including otherwise hidden barriers such as the one which surrounded Konohagakure. The holder of these eyes have the potential to completely master all five basic nature transformations that form the basis of ninjutsu. It can also decipher more of the Sage of the Six Paths' tablet than the Sharingan and the Mangekyō Sharingan are able to. The Rinnegan can also allow its user to summon and control the Demonic Statue of the Outer Path.

One of the Rinnegan's trademark techniques is the Six Paths Technique, which grants the user multiple abilities, known as Paths. The Animal Path can summon several different creatures. The Naraka Path can summon the King of Hell, which could be used for interrogation and restoration. The Preta Path can absorb any chakra-based ninjutsu. The Asura Path can clad the user in mechanised armour and grant them various weapons. The Human Path can read minds, at the cost of ripping out the victim's soul. The Deva Path allows the manipulation of gravity-based forces to either repel or pull in an enemy.

Finally the user is granted the Outer Path, also known as the seventh Path. It granted the user control over life and death. It can be used to control tailed beasts in a similar fashion to the Sharingan and the Wood Release with its chakra chains. The Outer Path also granted a shared field of vision between its user and their summoned creatures and Six Paths of Pain, which gave multiple angles of vision and neutralised any blind spots. At this point all of their eyes would also sport the Rinnegan.

When he was crippled by Hanzō, Nagato developed the Six Paths of Pain where he uses his Rinnegan and chakra receivers on freshly killed corpses to serve as extensions of himself. By doing so, Nagato could see each body's field of vision simultaneously, coordinating them with extremely precise planning. Nagato would also channel one of the abilities of the Six Paths Technique through each corpse.

Weilder(s)(Limit 2):

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Sharingan
The Sharingan ( Literally meaning "Copy Wheel Eye") is a dōjutsu kekkei genkai, which appears in some members of the Uchiha clan. The Sharingan is also called "Heaven's Eye", because of the many abilities it grants the user. Tobirama Senju defines it as the "eye that reflects feelings".

The Sharingan's abilities consist of two parts: the "Eye of Insight"  and the "Eye of Hypnotism". The first of the Sharingan's powers is being able to see the flow of chakra. The Sharingan itself gives colour to chakra, allowing the wielder to differentiate them. They are also able to tell if a person is under a genjutsu because the person's chakra flow would be irregular. The Sharingan's second-most prominent ability grants the user an incredible clarity of perception, allowing them to easily recognise genjutsu and different forms of chakra, though not to the same extent as the Byakugan. This also allows the user to pick up on subtle details, enabling them to read lip movements[7] or mimic something like pencil movements. As the Sharingan evolves, gaining more tomoe, this ability extends to being able to track fast-moving objects before finally giving some amount of predictive capabilities to the user, allowing them to see the image of an attacker's next move from the slightest muscle tension in their body and counter-attack or dodge without any wasted movement. However, even though the user may be able to see an attack or know it is coming, their body may not always have time to react.

The Sharingan's third and most well-known ability is that it grants the user the ability to copy almost any technique that he or she witnesses, apart from other kekkei genkai techniques. The user can memorise ninjutsu, genjutsu, and taijutsu with near-perfect accuracy, allowing the user to use the techniques as their own, or even modify them to create their own new techniques, much like Sasuke Uchiha's Lion Combo. In order to reproduce a copied technique, 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 hadn't trained nearly as much as Lee had. In addition to physical skill and kekkei genkai techniques, the Sharingan cannot reproduce techniques dependent on other factors, such as summons that the user has not signed a contract with.

The Sharingan's final commonly-used ability is capable of inducing a unique brand of hypnosis that involves suggesting actions and thoughts to the opponent through genjutsu cast by simple eye contact between both parties. More advanced Sharingan users can take the hypnosis ability even further to the point where a powerful summon like Manda or even a tailed beast may be controlled. When this was used against Manda and the Nine-Tails, their eyes took on the tomoe pattern of the users' Sharingan while under hypnotic influence.

The hypnotic ability coupled with the other aspects of the Sharingan can make the user appear as if they can "see the future". First, the user must perfectly mimic every move their opponent makes and possibly their thoughts and words through careful observation. Then, they suggest an action to the opponent such as hand seals for a technique that the opponent and Sharingan user already know and copy that. With these things done, the user can complete the action even before the opponent does, possibly using the Sharingan's genjutsu to confuse or delay them. As with other genjutsu, genjutsu cast by the Sharingan are capable of putting an opponent to sleep, inducing paralysis, replaying memories to someone else via genjutsu, or creating various illusions to deceive someone. The potency of the Sharingan's illusion is dependent on the user's knowledge and skill with implementing genjutsu. Two Sharingan users are also able to free each other from other forms of genjutsu by first using genjutsu on each other, allowing them to enter their comrades mind and free each other from the genjutsu.

In addition, more rarely used by the Uchiha clan, the Sharingan can allow the user to perform two very powerful and unique genjutsu: Izanagi and Izanami, which alters or decide one's destiny, respectively. Using Izanagi, the user can warp reality for a short amount of time, changing reality into illusion and illusion into reality, thus escaping death and rewriting destiny; although to make use of this technique to its full extent, the user must have the DNA of both the Uchiha and Senju. Izanami, on the other hand, is a genjutsu that traps the victim in an infinite loop disregarding their five senses; this technique was specifically created to counter anyone who would abuse Izanagi's ability to alter their destiny, by forcing the victims to relive the situation over and over until they accept it and cease using Izanagi. Both techniques have been labelled kinjutsu, because use of either causes the eye that performed Izanagi or Izanami to close forever.

Although the Sharingan consumes the user's chakra while active, the amount of chakra that the user must exert is so insignificant that they can keep it active constantly.

Mangekyō Sharingan:
The Mangekyō Sharingan is distinguished from a normal Sharingan by its appearance, which changes the form of the tomoe seal. Unlike the Sharingan, the appearance of the Mangekyō Sharingan differs from user to user with all known wielders of the dōjutsu having eyes that resemble variations of pinwheels.

The Mangekyō Sharingan gives the user access to several powerful techniques, with each user awakening different abilities. These include the powerful fire technique Amaterasu, the almost unbreakable genjutsu Tsukuyomi and, in rare cases, the use of Susanoo. Some wielders awaken the same technique in both of their eyes, such as Obito Uchiha, whose eyes allow the user to use space-time ninjustu such as the dimension-shifting technique Kamui, as well as Shisui Uchiha, whose eyes are both capable of activating Kotoamatsukami. Using the Mangekyō Sharingan puts strain on the user's eyes and erodes their vision, eventually causing blindness. This can be prevented by transplanting another pair of Mangekyō Sharingan from a close relative, such as a sibling. The newly acquired Mangekyō Sharingan looks like a merge of both eyes and is dubbed the Eternal Mangekyō Sharingan

Obtaining:
The Sharingan needs to be activated by the user when they are faced with a difficult circumstance or placed under emotional stress.

Sharingan Weilders:

Mangekyo Weilders((Limit 2 for now)):

Eternal Mangekyo Weilders((Limit 1 for now)):

All information received from http://naruto.wikia.com/wiki/Narutopedia