Revolutions are explosions of frustration and rage that build over time, sometimes over decades. Although their political roots are deep, it is often a single spark that ignites them — an assassination, perhaps, or one selfless act of defiance.
Feb. 26, 2011 A protester wearing a Tunisian flag makes his way past closed shops in the casbah toward sporadic gunfire in Tunis. Tunisia's revolution set off other protest movements across the Middle East. Nikki Kahn/The Washington Post Buy Photo