The fontanelle refers to the two bony “skylights” at the top of the head and the back of the occiput at birth, medically known as the “fontanelle”. It is the largest intersection of bones in the skull, and because there is no bone here, it is slightly sunken and softer to the touch than the rest of the head. When you put your finger lightly on the fontanelle, you can feel a pulse in line with the pulse, which is caused by the change in cerebrospinal fluid pressure in response to the pounding of the heart. When babies are born, the fontanel is about 1.5-2 cm, the first few months the head circumference grows fast, the fontanel also becomes bigger, about 6 months when the maximum reaches 2.5-3 cm, later as the skull gradually ossify, the fontanel gradually becomes smaller, about 1 year to 1.5 years old closed. The posterior chimney is located at the back of the baby’s head, at the intersection of the occipital bone and the two parietal bones, and is small in size, sometimes not even palpable. The posterior chimney gate is nearly closed at birth, or can only accommodate the fingertips, and closes about 2-4 months after birth. The early or late closure of fontanelle is one of the main indicators of cranial development and brain development. Either too early or too late closure is a sign of abnormality. The normal head circumference of a baby is about 850px at birth and 1075px at half an age. If it is less than 90% of normal, the child may have microcephaly or underdeveloped brain. MRI (magnetic resonance imaging) to determine the development of the brain. If the fontanelle does not close after 18 months, it is too late. It is common in babies with rickets, but there may be other diseases such as hydrocephalus. When normal, fontanelle is flat and slightly depressed in the standing position. However, if the baby vomits more frequently or has a lot of diarrhea, a large amount of water loss in the body can cause a sunken fontanelle; meningitis, encephalitis, vitamin A overdose, high fever, etc. can cause a full or raised fontanelle. Therefore, when your baby has fever, vomiting or diarrhea, you should pay more attention to the change of fontanel, and you should go to the hospital immediately to see a doctor if it is sunken or bulging. Since fontanel is not covered by hard skull, its surface is the scalp, and below it are the meninges, brain, and cerebrospinal fluid in order, so care should be taken to protect the brain from damage. Some people think that fontanelle is too fragile to be washed, and some even think that fontanelle cannot be touched and will become mute if touched. These statements are not based on science. If your baby’s fontanelle is not washed for a long time, it will easily accumulate dirty black scabs, which is very unhygienic and easily infected. Therefore, the fontanelle should be washed like any other part of the scalp, but when washing it, you should be gentle and try not to scratch it with your fingers, especially if your nails are too long to scratch your baby. The water should not be too hot, but warm. Some infants have some yellowish brown greasy scales on their fontanel scalp, is infant seborrheic dermatitis, can be sterilized cotton with some paraffin oil on the scales, to be softened and then gently wiped away with sterilized cotton, because the baby’s skin is delicate, must not be forcibly uncovered, otherwise it may cause skin damage. This disease can heal on its own, as long as there is no infection can not have to apply anything, when washing hair, it is advisable to use a neutral soap with little irritation or baby bathing milk.