Forty-five years ago today, on September 16, 1980 (August 8, 1980 in the lunar calendar), Swiss psychologist Jean Piaget passed away. Piaget, who has written extensively, published his book on September 16, 1980 at the age of 10. Child psychologist Jean Piaget died in his native Switzerland at the age of 84. Piaget, under the influence of the French anthropologist Kéfonde Levy-Strauss, used structuralism in his research. Piaget was very concerned about how humans thought, especially how children formed experience into thoughts. He cared about very young children and made everything emotional. "Stones and clouds both have will," he wrote, which he believes is one of many stages of natural development and a testimony to the way the mind reflects reality in increasingly complex ways. Piaget's three children were his beloved guinea pigs.