HOW UCHIHA MADARA OBTAINED THE ULTIMATE DOUJUTSU(RINNENGAN)

Before the era of ninja villages, Madara was considered one of the most gifted members of the Uchiha clan alongside his younger brother Izuna Uchiha. Madara also competed with Izuna as training. Even by his clan's standards, Madara's chakra was especially strong. As a child, Madara met Hashirama Senju for the first time and became rivals at skipping stones. With their first meeting cut short after discovering the body of a member of the Hagoromo clan, the two would later meet again and Madara questioned Hashirama revealed that his brother had been killed in battle. Telling Hashirama that he himself once had four brothers, the pair discussed the prospect of peace for the world. It was here that Madara was finally able to skip his rock to the other side of the river. As they grew older, Madara's rivalry with Hashirama increased, and the two would meet by the riverbank, where they would spar and talk about changing the future. On one such occasion, Hashirama brought up the prospect of creating a village where children would not be sent to war and could grow up to be strong warriors.

Madara awakens his Sharingan.

These meetings were not to last, however, as Madara's father Tajima soon found out about the two boys meeting and planned an ambush. However, the two boys warned one another in time, and as they fled, their fathers and brothers confront one another. After the initial scuffle, Madara and Hashirama intervened, getting between their respective families. Madara, realising that he had to chose between Hashirama and their dream or his family, regretfully decided to end his friendship with the young Senju, determined to protect his brother Izuna. Hashirama tried to make Madara reconsider, but Madara refused to let go of his anger for the Senju. He announced his full name to Hashirama, awakening his Sharingan.

Madara and Hashirama clash on the battlefield.

From then on, Madara would constantly battle Hashirama with the intent of erasing him from his past. Eventually, he and Izuna awakened the Mangekyō Sharingan. With their newly obtained power, the two brothers became the head of the clan, with Madara becoming its leader. Sometime afterwards, Madara and Izuna fought Hashirama and Tobirama, where Izuna was mortally wounded by Tobirama. Madara retreated and Izuna died from his wounds but left Madara his eyes, granting him the Eternal Mangekyō Sharingan.Madara later confronted Hashirama again with his new found ocular prowess, but nonetheless, after a day-long battle, he was finally defeated. Noting that he could not trust them any more, Madara told Hashirama that the only way to regain this trust was to either kill himself or his brother. When Hashirama resolved to kill himself, Madara stopped him, noting his courage and accepted the truce.

Konohagakure is formed.

The Senju, the Uchiha, and all the clans they had conquered came together to form the ninja village Madara and Hashirama once dreamed of together. Ultimately, it was Madara who named the village Konohagakure. Madara's relationship with Hashirama steadily became much like from their childhood, sharing their ideas and hopes. When Hashirama told Madara about the plans for the village leader, who would be known as the Hokage, he wished to give the title of Hokage to Madara. Tobirama, however, noted that this should be a democratic decision and not a unilateral one, citing that in any case, the villagers would never accept Madara as such. Madara, who was spying on the Senju siblings, began to grow uneasy from this lack of trust, doubting the worth of this village. During the time he was a shinobi of Konohagakure, Madara approached Mū and Ōnoki where he informed them that despite the alliance that Iwagakure had made with Konoha, his village was to remain the dominant power and that from that point on, they would obey Konoha.Afterwards, Madara fought and defeated them when they engaged him in battle.
Later, Hashirama would instead be elected as Hokage and at the Naka Shrine, Hashirama expressed his wish that Madara inherit the title of Second Hokage once the villagers started seeing him in another light, however, Madara noted that Tobirama would more than likely inherit that title, and that when he did, it would not bode well for the Uchiha. Later meeting in the Naka Shrine, Madara told Hashirama his intent on leaving the village and he had a plan to make his dream become a reality while at the same time, falling victim to the Curse of Hatred once again. Hashirama tried to convince Madara to let him help his childhood friend, but Madara scoffed at Hashirama's attempt to follow him, saying that no one can get behind him.

Madara with the Nine-Tails battling Hashirama

Abandoned by his clan, Madara left the village, sought out Kurama, and subdued it using his Sharingan. He later returned in order to challenge Hashirama in battle, fighting at the site that would someday be called the Valley of the End. The battle waged well into the night, leaving both shinobi battered and exhausted and Madara stripped of his control over Kurama. With both of them too weak to use their strongest techniques anymore, they made one final clash, leaving Madara the one standing and looking down over Hashirama in victory. However, due to not having enough chakra to access his Sharingan, Madara couldn't tell that the defeated Hashirama was actually a clone, and was shocked to find the real Hashirama standing behind him and stabbing him through the chest. Quickly losing consciousness, Madara vowed that one day Konohagakure would be shrouded in darkness, and appeared to have died from his wound.
Possession of Kurama was completely taken from him by Hashirama's wife, Mito. In spite of this, Madara survived the stab wound given to him by Hashirama and went into hiding. He then used Hashirama's cells, which he had acquired on the battlefield, and transplanted them into his wounds. Though he noted that nothing happened at first, when he was nearing the end of his natural lifespan, he awakened the Rinnegan.He also acquired the Wood Release kekkei genkai, and with both Senju and Uchiha DNA — with that he had the ability to summon the Demonic Statue of the Outer Path.He later transplanted his Rinnegan eyes into Nagato without the young man knowing,and replaced his left eye with a spare Sharingan.Years later, Madara had been reduced to using the Demonic Statue of the Outer Path as a life support system, constantly being supplied chakra by it or else he would die immediately.Also from the stolen cells of Hashirama, Madara used the statue to cultivate a living clone of Hashirama.

An elderly Madara speaking with Obito.

During the Third Shinobi World War, he saved Obito Uchiha after the battle of Kannabi Bridge, using artificial mass to replace the destroyed half of Obito's body.He told Obito that he would have to repay his debt to him slowly.Madara then left White Zetsu and a spiral-patterned clone with the task of guarding Obito and helping him with his rehabilitation, so he could be useful to him by the time he woke up. After Obito returned to him as he had predicted, Madara, now certain that Obito was sincere, carried him into a genjutsu and told him about the Sage of the Six Paths and the Ten-Tails. He then explained how he had awakened the Rinnegan, gained access to the empty shell of the Ten-Tails, and cultivated Hashirama's cells.He would go on to teach him among other things various kinjutsu, advanced Uchiha techniques, the Yin–Yang Release, and the power of the Rinnegan. Before passing, Madara also created Black Zetsu by pouring his will into White Zetsu and also left part of his will in the chakra receiver which extends from the statue's navel. With that, Madara disconnected himself from the statue and, with his dying breath, told Obito to go and, until the time he was revived, he was to act under his name.
Fulfilling the legendary Uchiha's request, Obito, now known as "Tobi", began operating under his name while concealing his face. Due to his first-hand knowledge of Madara's actions and deeds, other shinobi were led to believe he was in fact the legendary ninja himself. However, thanks to researching the matter with Orochimaru, Kabuto Yakushi learned the truth behind Madara's time after the Valley of the End and actual death, reincarnating the ninja to blackmail Tobi into letting him aid him during the Fourth Great Shinobi World War where Kabuto partly exposed Tobi's deception.