We are presently in the period of the fifth sun, but what were were the earlier periods like?
The first of the five suns was the Sun of the Ocelot. At that time the world was shrouded in darkness and humans lived by animal instinct alone, without the benefit of reason. Lacking thought, they were eventually all eaten by ocelots. The second sun was the Sun of Air, a world of spirits and transparent beings that may return some day. But the humans of this time did not understand the necessary principles to be redeemed from their sins and the gods changed them all into monkeys.
The third was the Sun of Fire. During this period, people were ignorant of the gods. All the rivers dried up and all creatures were killed by roaring flames, with the exception of the birds, who flew to safety. The fourth sun was the Sun of Water, Tlaloc, the rain god, who destroyed all the people in a flood.
The fifth is our own period. This is the sun where the other four principles, animal energy, air, fire, and water, are combined and in balance. We cannot take it for granted that this sun will last forever; our continued existence is dependent upon following the "ladder of redemption" that is contained in the Aztec calendar and observing rituals. If the gods are again ignored, then this sun too will die and all of us with it.