Newborns can have an unconscious smile at birth, a conscious smile at 1-2 months of age with teasing, and most children can laugh after 3 months of age with parental teasing. A newborn baby can show an unconscious smile with the corners of the mouth raised and the eyes curved into a crescent shape. The first strictly conscious smile occurs at about 4-6 weeks of age, and some infants may smile earlier, but it disappears in a flash. As they get older, most babies can smile at 2-3 months of age, but the exact timing depends on the family environment and the child’s growth and development, so as long as it is within the normal range, there is no need to worry too much. Therefore, when a child has a conscious smile, parents need to actively educate their children, find out what they like through their expressions, and take them out more often so that they can have contact with society, which is beneficial to promote the balanced development of all systems and organs.