Even though trick-or-treaters flooded the streets of Chicago on Halloween, many soon prepared to celebrate a rich cultural tradition that originated in Mexico: Día de los Muertos.

Día de los Muertos, or Day of the Dead, is a two-day celebration that aims to reunite the living and the dead and is often seen as a celebration of life for deceased loved ones.

Unlike most funeral ceremonies surrounding death, Día de los Muertos is considered an annual occasion during which the deceased ceremoniously return to their families.

One of the most recognizable features of Día de los Muertos celebrations are colorful skulls, often depicting death in a lighthearted and humorous way.

From sugar candies and clay decorations to face paint, skulls or calaveras are the most ubiquitous part of the tradition.

Celebrations begin at midnight on November 1 with “Día de los Angelitos,” or “Day of the Little Angels,” when loved ones who died as children are supposed to be reunited with their families for 24 hours.

During this time, the child’s favorite snacks, toys and photos are placed on an altar, called an ofrenda, to encourage the deceased children to visit. Children’s names are often written on a sugar skull.

At midnight on November 2nd, “Día de los Difuntos” is celebrated to remember loved ones who have passed away.

While the night is often a lighthearted celebration full of laughter and memories, the ofrendas for Día de los Difuntos have a much more adult theme, often serving tequila, mezcal and pulque while playing games together.

The climax of the celebrations begins on November 2nd at 12:00 p.m., when Día de los Muertos is officially celebrated and the spirits of all those who have died are remembered.

This part of the celebration is public and often includes celebrations in cities with parades and calavera-painted faces in living memory of loved ones.

Cemetery visits are also common during this part of the holiday, when marigolds, gifts and sugar skulls with the name of the deceased are placed next to the gravestone.

At this time it is also customary to clean the gravestone of the deceased and restore it to its original color.

According to the National Museum of Mexican Art in Chicago, Día de los Muertos began in the last 500 years as a combination of ancient indigenous cosmology and Roman Catholic tradition.

This year’s Día de los Muertos exhibition at the museum, titled “Where the Past is the Present,” is dedicated to Ray Patlán, a Chicago muralist and painter who died in April of this year, the museum said.

“Art is a reflection of society, and this exhibition commemorates all those who have died as a result of violence,” the museum said in a post.

The museum is located at 1852 West 19th Street in Chicago’s Pilsen neighborhood.