Unit 1 Stages of lifeVersión en línea Unit 1 Stages of life por Mariam Domingo 1 Childhood 2 Adolescence 3 Adulthood 4 Old age From 0 to 12 Newborn babies drink their mother's milk Milk teeth fall out and permanent teeth appear. Between 12 and 16. Boys and girls go through different changes. Your body is fully-developed You are ready to have children You become more frail and weaker. You have more experiences, memories and knowledge.