Tomorrow (Oct. 31) is Halloween, a holiday that has its roots in Celtic culture but is celebrated all over the world today.

Long ago, the Celts (whose descendants include the Irish, Welsh, Scots and Bretons) had a Samhain, a night when the spirits of the dead were set free to roam the earth. Bonfires were lit to give light to the spirits so they could find their way back to the world of the dead. People also dress up in costumes that scare away the spirits and keep them away from their bodies. Food was also put out for these spirits who might come to harm.

Today, people still celebrate Halloween on October 31 by lighting bonfires, dressing up in fancy costumes, and distributing food (mainly candy). The holiday is beloved in the United States and around the world.