The events in Iran are a perfect example of a systemic process at work. A stable state is one which is known in physics as "far enough from equilibrium", which means that the flow of energy through the system is sufficient to maintain the system but not too much to cause it to race uncontrollably to a bifurcation.
There is nothing unusual about what is going on in Iran. This is what underlies every situation in which observers wring their hands and wonder why the protagonists don't stop what they're doing. Why they don't pull back from the brink, The reason is that they cannot. When humans reach a certain point in their impetus for change, no amount of rationality can reverse the direction they are going in. As in physics, the momentum of energy in the system reaches a point from which it cannot reverse itself.
When observers say that this has been building for a long time, they are referring to elements of the process: discontent of various kinds among various groups of the population. In each of these groups, the energy has been steadily accelerating, until an event like a stolen election pushes the acceleration over the top.
We can expect more bloodshed in Iran. But also, as President Obama intuitively senses (or maybe he has studied systems), a new situation is being shaped by what is happening. Men cannot control the process, but the process itself is a forward motion. Not necessarily better, but certainly different. A bifurcation point leads to a new system, which can be either more or less organized than the preceding one: it can lead to anarchy, or totalitarianism. Eventually the system will evolve to a higher level of organization and civilization.
The fundamental difference between the Shi'a and the Sunni is one of class. The Shi'a believe in egalitarianism, the Sunni believe in a class society. When participants in today's events say they are not interested in the Western interpretation of freedom, do not think they are paying lip service to the regime in power. They want freedom with equality, not what we call "freedom of opportunity" which, as one famous revolutionary told me many years ago, means freedom to be hungry.
And if many of the Iranian women, who play such a crucial part in this saga, are wearing headscarves, it's also in homage to the Prophet, for whom women were equals.