Child development

Child development involves the biological, psychological and emotional changes that occur in human beings between birth and the conclusion of adolescence. It is—particularly from birth to five years— a foundation for a prosperous and sustainable society.
Childhood is divided into three stages of life which include early childhood, middle childhood, and late childhood (preadolescence). Early childhood typically ranges from infancy to the age of 6 years old. During this period, development is significant, as many of life's milestones happen during this time period such as first words, learning to crawl, and learning to walk. Middle childhood/preadolescence or ages 6–10 universally mark a distinctive period between major developmental transition points. Adolescence often begins around the onset of puberty, marked as menarche or spermarche, occurring between 10 and 12 years of age, and ends upon acquiring the age of maturity. Adolescence is characterized by maturation of the body, increase in capacity for learning, and emergence of personal identity. Developmental change may occur as a result of genetically controlled processes, known as maturation, or environmental factors and learning, but most commonly involves an interaction between the two. Development may also occur as a result of human nature and of human ability to learn from the environment.
There are various definitions of the periods in a child's development, since each period is a continuum with individual differences regarding starting and ending. Some age-related development periods with defined intervals include: newborn (ages 0–2 months); infant (ages 3–11 months); toddler (ages 1–2 years); preschooler (ages 3–4 years); prime childhood (ages 5–8 years); preteens (ages 9-12 years); and teens (ages 13–19 years).
Parents play a large role in a child's activities, socialization, and development; having multiple parents can add stability to a child's life and therefore encourage healthy development. A parent-child relationship with a stable foundation creates room for a child to feel both supported and safe. This environment established to express emotions is a building block that leads to children effectively regulating emotions and furthering their development. Another influential factor in children's development is the quality of their care. Child-care programs may be beneficial for childhood development such as learning capabilities and social skills.
The optimal development of children is considered vital to society and it is important to understand the social, cognitive, emotional, and educational development of children. Increased research and interest in this field has resulted in new theories and strategies, especially with regard to practices that promote development within the school systems. Some theories seek to describe a sequence of states that compose child development.