There are six main stages of the human life cycle, during which a human is a fetus, baby, child, adolescent, adult and elderly person. The exact age for entering each stage varies, but all healthy humans follow the same life cycle stages.
The fetal stage occurs when a human is growing inside the mother's womb. During this time, the embryo grows and develops until it is ready for birth. After around nine months, the fetus is born, and the baby stage begins.
After one or two years, the baby stage is completed, and the childhood stage begins. During this stage of human development, the child begins to learn how to walk. The child’s speech also rapidly improves during this time.
When a child starts puberty, the adolescent stage begins. This stage is also called the teenage years and usually occurs between the ages of 13 and 19. A person going through the adolescent stage experiences a number of changes in body and mind, which can make it a confusing stage of development.
The adult stage begins when the body is fully developed. This stage continues for many years, until old age begins. There is no set age for when old age begins, as there isn’t a physical process or change that defines it. Most people consider old age to begin at some point between 60 and 70 years old.