Celebrations of Día de los Muertos, which can be traced back to Mayan and Aztec times, have one thing in common — remembering and honoring the dead.

Building an altar, often referred to as an ofrenda, is one of the most common ways to mark Día de los Muertos.

Thelma Muraida, a longtime altar builder, and scholars at El Instituto Cultural de México explain the meaning behind items traditionally used on Día de los Muertos altars.

There are two aspects to building an altar — communication with those who are no longer physically with us and the acknowledgement that there is an afterlife. The light from candles and the strong aroma of marigolds and incense help guide spirits home.

Glasses of water and pan de muerto are used on altars to nourish the spirits on their journey. Although spirits cannot eat, says Muraida, they can absorb the essence.

Papel picado in the colors purple (for pain), white (for hope) and pink (for celebration) are commonly used on altars to symbolize the life and afterlife of the person being remembered.

Altars are built in tiers to symbolize the steps, or journey, that spirits take. The tiers of an altar are built like a pyramid with the highest tier being the smallest.