One of the customs practiced is to use skulls in each of the festivals, either as decoration or simply inside an altar.

These images in the form of skeletons are used as representations that serve as a memory of those beings that are no longer in this world. Each skull represents a family member who passed, as well as serve as placement for loved ones who are not in photographs. 

On the other hand, they serve to emphasize the importance of accepting death as part of human existence. Which means, in other words, that life is fleeting and you have to live it knowing that there is always an end.

Skulls usually vary in size and are made from sugar or as sculptures made with fine materials. Some also often use them as part of their costumes, as seen in catrinas.