Tucked inside the gummy, toothless smile of an infant is a small piece of tissue under their upper lip called the labial frenulum.
"Frenulum" is the term used to describe a band of tissue that attaches two structures, and the labial frenulum is the specific attachment on the inside of the upper lip that connects to the upper part of the gums, just above the front teeth, according to a study in Global Pediatric Health. If you pull up your upper lip, you will be able to see this thin band. All babies are born with this, but the level of the attachment to the gums varies between individuals. In general, according to the Global Pediatric Health study, younger children have a more prominent frenulum than older children.