Activation of sharingan and it's advancing.
The Sharingan is the Uchiha clan's bloodlimit, although it's a blood limit not all Uchiha clan members have the Sharingan, they have to feel a special kind of emotion "be it agony, despair or revenge" to unlock the Sharingan's first level the 1 tomoe and begin advancing in the Sharingan levels, The Sharingan consists of 2 parts The eye of Insight and The eye of Hypnotism, first level is the 1 tomoe Sharingan, in this stage the Sharingan user is able to follow speeds that are untraceable with the normal eyes, such as Haku's speed when he's using the Ice demonic crystal mirrors, the user is now able to pierce through D-rank genjutsu, when the Sharingan user gains more skill the Sharingan level rises "however that's in the anime not in nb" the user reaches the second level of the Sharingan the 2 tomoe, which it's main power is seeing chakra, the Sharingan eye itself gives different colors to different forms of chakra allowing the user to differentiate them, and the second power is being able to trace speeds higher than in the 1 tomoe level could track, it gains a new power alongside seeing chakra which is predicting Taijutsu movements and reading handseals, the Sharingan eye can read the Taijutsu movement patterns and allow the body to react to them when it's in the range of speed that the 2 tomoe Sharingan is able to track and the last power is being able to read the opponent's handseals and know what technique he is going to use and from which element before the opponent even performs them, the user now is able to break through C-rank and below genjutsu techniques. when the user gains much more skill he acquires the third and last form of the normal Sharingan, the 3 Tomoe Sharingan, like the two previous stages the 3 tomoe Sharingan is able to track speeds higher than the previous Sharingan stages, it's able to track speed equivalent to the 2nd gate of the eight inner gates, and is able to predict Taijutsu movements faster and read through handseals faster than the 2 tomoe Sharingan is able to, the new power is that the user is able to cast genjutsu techniques based on eye contact with the enemy which is the fast form of genjutsu but has the drawback of having to look in the enemy's eyes for it to work and sometimes the enemy has to be looking directly at your Sharingan eyes for the genjutsu to take effect, now the user is able to pierce through B-rank genjutsu techniques and lower.