A dimple, also called a gelasin (, ) is a small natural indentation in the flesh on a part of the human body, most notably in the cheek. Numerous cultures believe that cheek dimples are a good luck charm that entices people who perceive them as physically attractive, but they are also associated with heroism and innocence, which has been included in literature for many centuries. Medical research debates whether cheek dimples can be inherited or which type of allele they are, but it is certain that humans with cheek dimples are more likely to have them in both cheeks. Depth and length appearances are affected by the shape of the skull and dimples can appear and disappear due to age. There are four types of facial dimples, including cheek, and the cleft chin (sometimes nicknamed a "chin dimple"). Overview Cheek dimples when present, show up when a person makes a facial expression, such as smiling, whereas a chin dimple is a small line on the chin that stays on the chin without making any specific facial expressions. Dimples may appear and disappear over an extended period; a baby born with dimples in their cheeks may lose them as they grow into a child due to their diminishing baby fat. Anatomy Dimples are usually located on mobile tissue, and are possibly caused by variations in the structure of the facial muscle known as zygomaticus major. Specifically, the presence of a double or bifid zygomaticus major muscle may explain the formation of cheek dimples. This bifid variation of the muscle originates as a single structure from the zygomatic bone. As it travels anteriorly, it then divides with a superior bundle that inserts in the typical position above the corner of the mouth. An inferior bundle inserts below the corner of the mouth. Cheek dimples can occur in any person, but some studies have suggested that dimples (both cheek and chin) are more common in females. They can be either permanent, or transient (aging makes dimples appear/disappear due to facial development and muscle growth): a Greek study spanning almost 20 years concluded that 34% of Greek adults had dimples whereas 13% of Greek youths (between 7 and 15 years old) had dimples as well, which might suggest that transient dimples are more common than permanent. Professor John McDonald, citing limited research, concluded that dimples have been mislabeled as genetically inherited and as