Today's mix of parties, pranks, and profit is a far cry from Halloween's ancient origins. Over the centuries the celebration has seen a lot of changes, and we've summed them up here for you.

Halloween's origins date back more than 2,000 years. On what we consider November 1, Europe's Celtic peoples celebrated their New Year's Day, called Samhain (SAH-win).

On Samhain eve—what we know as Halloween—spirits were thought to walk the Earth as they traveled to the afterlife. Fairies, demons, and other creatures were also said to be abroad. (See pictures of crypts and catacombs.)

In addition to sacrificing animals to the gods and gathering around bonfires, Celts often wore costumes—probably animal skins—to confuse spirits, perhaps to avoid being possessed, according