And these are examples of what a Mayan glyph looks like. So that is a Mayan glyph, and you read it in an order like this. And once again, this is a very early form of writing, and it's believed to be the first form of writing, well-established writing, in the Americas. Now, on top of their sophisticated numeral system and the writing that they developed, they also had a very sophisticated calendar. Their calendar was more accurate than the Julian calendar, which was adopted by Julius Caesar, and that was the state of the art in the Western world until the middle of the second millennium. So their calendar was more accurate than what was used in most of the world until around 15 or 1600. Now, as we get into 250 in the Common Era, that's considered the Classical Period.