How do you spawn the Ender Dragon?

How do you spawn the Ender Dragon? Players can re-summon the ender dragon by placing four end crystals on the edges of the exit portal, one on each side. When the dragon is re-summoned, the four end crystals point to the tops of each pillar setting off a series of explosions that resets the obsidian pillars, iron bars, and end crystals.

Players can re-summon the ender dragon by placing four end crystals on the edges of the exit portal, one on each side. When the dragon is re-summoned, the four end crystals point to the tops of each pillar setting off a series of explosions that resets the obsidian pillars, iron bars, and end crystals.