The Sharingan is one of the 3 great dojutsu's in Naruto, and the one that the Uchiha have the ability to awaken. It has two parts; the eye of insight and the eye of hypnotism. Sharingan users can see chakra flow, and they perceive them as different colors depending on the person. With the Sharingan, one can see if someone is caught in a Genjutsu due to the chakra flow being irregular. The second ability of the Sharingan grants the user an amazing clarity of perception. Because of this, they can easily recognize Genjutsu and different forms of chakra. Despite that, it is still not as advanced as the Byakugan when it comes to different forms of chakra and such. Subtle details are easily recognized through the use of the Sharingan, which allows one to read lip movements, as well as to copy movements to an extreme degree. It is able to see through thick fog and other things that would normally cloud the vision. When the Sharingan evolves, it gains a tomoe, with a Max of 3 Tamoe. The more Tamoe, the better the perception of movements, down to simple muscle twitches becomes exceptionally better. This makes their ability to predict the opponents next move much better. The third ability of the Sharingan allows the user to copy any jutsu it sees, aside from KG of course. Nin, Gen, and Tai are all easily recognized, memorized, and able to be copied with godlike precision. The last ability of the Sharingan allows the user to cast a enjoy tai on the opponent where he can then prompt them to say or do pretty much anything. This can also be done to a tailed beast or boss summon if skilled enough.
There are two forbidden techniques among the Uchiha known as Izanami and Izanagi. Izanagi was used to change reality into an illusion, and Izanami was used to decide fate, and was crates to stop users obsessed with using Izanagi. These powers come at a high risk; the loss of one eyes light.
The Sharingan mutation occurs when under extreme emotional stress or difficult circumstances.
The Mangekyō Sharingan mutation occurs when an Uchiha suffers the loss of someone very close to them. This doesn't always happen, however. Overuse of this causes the user's eyes to lose their light. The only way one can gain eyesight after, is to take a siblings Mangekyō and replace your own, giving the user the Eternal Mangekyō Sharingan. This Sharingan will never lose it's light due to overuse, and it eternal.