We humans tell stories to remember the truth. Most of them speak of important characters, of powerful beings; but there are also epic stories that recount the feats of creatures more like us — less in the spotlight, yet just as important.

Everyone knows, for example, that an eagle landed on a nopal cactus growing on a small islet in the middle of a great lake, to devour the serpent it carried in its talons. What almost no one knows is how the nopal got to the islet in the first place. This would be no feat at all if nopales could fly — but no: where a nopal is born, it dies. This nopal must have been extraordinary. And it matters, because without that nopal, the story of the eagle and the serpent cannot be told.

As happens to many of us, at first the nopal didn't know its mission was as important as the eagle's. Only later would it realize that it was the nopal itself that set in motion the chain of events that allowed the eagle to fulfill its destiny. It sprang from a seed that a bird carried there a couple of years before March 13, 1325 — the date when the other actors of the story arrived right on time for their appointment with destiny, to found the great Tenochtitlan: the eagle, the serpent, and the Mexica people.