All over Mexico, ofrendas or altars are set up in homes and cemeteries on Oct. 30 and 31. They are covered with flowers, fruits, vegetables, candles, incense, statues of saints, photos of the deceased. The sky is represented by a sheet or strings of paper cutouts. Traditionally, the flowers used are marigolds, and the incense used on the altar is copal, the resin from a particular tree. Like moles and chile-laced dishes prepared for some of the ancestors, the flowers are quite aromatic and the copal has a distinctive smell. The aromas are used or consumed by the spirits, which, like the scents, can't be seen. The foods are eaten (or given away) by the living later, after their essence has been consumed.
The use of skulls is inherited from the Aztec ritual. The Aztecs and other Meso-American civilizations kept skulls as trophies and displayed them during the ritual. The skulls were used to symbolize death and rebirth.
The skulls were used to honor the dead, whom the Aztecs and other Meso-American civilizations believed came back to visit during the monthlong ritual.
Today, people don wooden skull masks called calacas and dance in honor of their deceased relatives. The wooden skulls are also placed on altars that are dedicated to the dead. Sugar skulls, made with the names of the dead person on the forehead, are eaten by a relative or friend.
The popular use of skelettons was also inspired from the work of Mexican press artist Jose Guadalupe Posada, who died in 1913. Posada inspired muralist Diego Rivera and others with his caricatures of the rich and political, all depicted as skeletons. Katarina, a skeletal figure in a plumed hat and dress, has become the instant visual signal of El Dia de Los Muertos.