The Popul Vuh teaches that humans, the gods' creation of the current Long Count cycle, were made from maize. (The creation of the previous great cycle, which was made of wood, spoke without understanding and so was condemned to spend this great cycle as monkeys.) We continue to acknowledge our origin by sustaining ourselves on tortillas, tamales, and atole even to this day, as our own Long Count comes to a close and we ponder our fate.
The historical role of atole as the agua de uso - the liquid taken throughout the day to slake thirst - has been declining as quickly as our farmland, while plastic bottles of brand-named reverse-osmosis city water have taken its place. Too plebeian for the fancy restaurants and too filling for the mainstream ones, atole now tends to be served primarily by aunts and grandmothers in remembrance of their rural childhoods. It is passing into a cultural symbol enshrined by clichés... If you're más viejo que el atole, you are even older than the hills. If you have atole en las venas, you're more unflappable than if you had ice-water in your veins. If you are dando atole con el dedo (serving atole with your finger), you are telling someone a story bit by bit, a sure sign of deceit.
Atole is made principally by boiling masa and water to the consistency of a thin porridge. By tradition it has been drunk instead of plain water, hot or cold, from calabashes throughout the day. It's now served in mugs as a comfort food and is most particularly trotted out for the festivities of First Communion, Christmastide (12 December to 6 January), and Candelaria (2 February). Variations include the addition of plum in Morelos and Guerrero, pineapple or coconut in Veracruz, cacao pod in Uruapan, blackberry in Michoacán; throughout the country strawberry, guava, nance, prune, walnut, capulín (Prunus serotina var. virens), almond, pumpkin, or tamarind might be added. The original recipes involve a lot of time and effort, so modern food science has made the more common atoles available in the instant-drink aisle of every Mexican supermarket. (There's a good chance, however, that people who hold to the powdered stuff will spend the next Long Count as Republicans.)