During the first 3 months of life, children are characterized by short sleep times and frequent naps because of the small amount of food, the number of meals and the short sleep cycle. They rarely sleep for more than 4 hours in a row, and there is no big difference between day and night. From the age of 3-6 months, children enter a stable sleep period where they can sleep for more than 5 hours continuously at night and wake up once or twice in between. However, some children always cry at night when they sleep and make their parents tired, why? It is suggested that parents can look for reasons from their children’s physical factors: (1) teething pain: children start teething from 5 months and grow all the way to two and a half years old, there will be discomfort due to teething. Observe the child’s cheeks and chin. If there is obvious drooling red rash, swollen gums, tenderness and slight fever, you can consider that it is due to teething pain bothering the child and causing sleep disturbance. Parents can use symptomatic methods to relieve their child’s discomfort. After the child’s teeth come in, the sleep will improve since then. (2) Children holding urine: Some children (especially boys) feel uncomfortable because they hold urine, making their bladders irritated by distension and pain, which can manifest as restless sleep and turning over back and forth (with crying). After urinating, the child will continue to sleep quietly. This is a sign that the child needs to urinate at night. Parents can help the child to urinate. (3) Nasal congestion: If the child has a large nasal crust in the nasal cavity, it will block the nasal cavity and force the child to breathe through the mouth. In this way, the dry air irritates the throat, causing discomfort such as coughing and causing the child to cry out suddenly. After the obstruction in the nasal cavity is removed, the child is able to continue sleeping peacefully. (4) Too hot or too cold at night: Because wearing too much cover makes the child irritable or stirring up the covers, followed by feeling cold, he or she will behave as grunting and crying.