Philtrum is the vertical gap between the border of the upper lip and the base of the nose. This is where three points of the human face connect and it is usually formed in the 3rd or 4th month of pregnancy.
The ittle grove is actually known as the philtrum and is a product of the way the human face develops
In human beings, the philtrum is formed at the place where the maxillary sinuses get fused together. A study that included boys with autism proved that the extended philtrum is one of the physical signs of autism.
These gaps never fuse during fetal formation so it remains between the upper lip and the nose. It usually does not cause any health issues, however women with extended philtrum sometimes do a corrective surgery. This surgery includes cutting a small portion between the nose and lips in order to fill the lips.
The philtrum is very important for better functioning of the sense of smell. It also transmits moisture and keeps the nose moist. In humans and the majority of animals the nose functions better when it is wet.
Watch Dr Mosley explaining this below, as well as see an astonishing video of the face as it forms in the womb and how all the pieces eventually come together to create a recognisable human face, taken from scans of a real baby developing.