What happened to obito Uchiha?

When his friend and crush Rin was captured by some enemies from the Rock Village, he went to save her, with a younger Kakashi. They found her in a cave and untied her after defeating a shinobi. While leaving, the shinobi did a rock breaker jutsu, causing a cave-in. Kakashi got hit and fell, and in an attempt to save him, Obito was crushed under a rock. Knowing he was going to die, he gave Kakashi his remaining Sharingan eye, since Kakashi had lost his eye in a battle just before.