How did Madara Uchiha survive such a long time? In the last chapters of the manga,


   When Tobi finally admits he is Obito and starts to remember what happened after the rock hit him, he meets Madara. How is this possible? Hundreds of years must have passed; how was he able to survive so long?
Madara, when he was close to death, awakened the Rinnegan.

The Rinnegan allowed him to break the seal placed by the Sage of the Six Paths, and summon the Juubi's shell (The Gedo Mazo) from the moon.

Using it as a catalyst, Madara used Hashirama's cells in order to extend his own lifespan.

Once disconnected from the Mazo, Madara died instantly.