The concept of children is relative to adults, and the current standard for adults is to reach the age of 18, so they generally belong to children until they are 18 years old. Specifically children can be subdivided into the following stages, these stages are mainly based on the different growth and development characteristics of children and delineated: 1, infancy: less than 1 week old belongs to the category of infants; 2, toddlers: 1-3 weeks old this range is the category of toddlers; 3, preschool: the child’s age between 3-7 weeks old, all belong to the preschool period; 4, school age: school age is the child more than 7 weeks old to Pre-adolescence; 5. Adolescence: Adolescence begins at about 10 weeks of age and lasts until about 18 years of age.