But when people refer to the Indus Valley Civilization in particular, they're usually starting around 3,300 BCE. And in orange right over here, this is the early period. Or you could say the early Indus Valley Civilization. Now some of the biggest structures and pieces of technology that have been discovered have been right over here which is often referred to as the mature, mature period for the Indus Valley Civilization. And then it goes into decline. We'll talk about why it might have gone into decline although we're not really sure. And this is called the late.