After spending his youth in Neuchâtel, Jean Piaget moved to Geneva in 1921, the city where most of his life and academic career would take place. He will marry a modern woman, Valentine Châtenay, from a family with a philanthropic and socialist tradition. They met at the Jean-Jacques Rousseau Institute in Geneva and were married in 1923. From this marriage will be born three children, Jacqueline, in 1925, Lucienne, in 1927 and Laurent, in 1930. Jean and Valentine will document their observations of these children’s development, setting the foundation for the seminal works of developmental psychology. From these observations three of the most important works of scientific psychology of the 20th century, were born (The origins of intelligence in children, 1936, The construction of reality in the child, 1937, and Play, dreams and imitation in childhood, 1945).