I already wrote about Piaget in the "IQ test origin" series. I will post here only the relevant part regarding his achievements as an young prodigy.
Jean Piaget was a precocious child who demonstrated a keen interest in animal life and an encyclopedic knowledge of biology and taxonomy. When he was ten years old, he began volunteering at the Neuchâtel Museum of Natural History. The museum's director, the seventy year-old naturalist Paul Godet, took him on as his assistant and apprentice, and paid him for his work by giving him rare specimens for his personal collection (Vidal, 1994). Piaget continued to work at the museum for four years, and his interest in the natural sciences continued to grow. His professional accomplishments in this area were numerous, beginning at age ten when he published a paper on the albino sparrow, and culminating with a doctoral thesis on the classification of mollusks when he was twenty-one. After completing his Ph.D., Piaget spent several months studying psychoanalysis at the University of Zurich. He was a promising student, and his contemporaries believed that he would eventually make important contributions to this field (Vidal, 1994). However, a serendipitous opportunity presented itself, and Piaget soon found himself working for Théodore Simon, co-author of the Binet-Simon intelligence scale. Simon placed him in Binet's laboratory, and set him to work standardizing Cyril Burt's reasoning tests on Parisian children. Piaget thought that the standardizing task was dull, and he never finished it. However, his clinical interactions with the children were not without interest. He began to notice that children of similar ages made similar types of mistakes, and it occurred to him that Simon, Binet and Burt might be asking the wrong question: Perhaps the key to understanding human intellectual development is not in what children get wrong, but how they get it wrong. It was clear to Piaget that childish reasoning is not merely less accurate than adult reasoning; it is qualitatively different (Wadsworth 1996). From this point forward, Piaget dedicated himself to answering the question "How does knowledge grow?" Piaget eventually came to believe that intelligence is a form of adaptation, wherein knowledge is constructed by each individual through the two complementary processes of assimilation and accommodation. He theorized that as children interact with their physical and social environments, they organize information into groups of interrelated ideas called "schemes". When children encounter something new, they must either assimilate it into an existing scheme or create an entirely new scheme to deal with it (Wadsworth 1996). Piaget also believed that intellectual development occurs in four distinct stages. The sensorimotor stage begins at birth, and lasts until the child is approximately two years old. At this stage, the child cannot form mental representations of objects that are outside his immediate view, so his intelligence develops through his motor interactions with his environment. The preoperational stage typically lasts until the child is 6 or 7. According to Piaget, this is the stage where true "thought" emerges. Preoperational children are able to make mental representations of unseen objects, but they cannot use deductive reasoning. The concrete operations stage follows, and lasts until the child is 11 or 12. Concrete operational children are able to use deductive reasoning, demonstrate conservation of number, and can differentiate their perspective from that of other people. Formal operations is the final stage. Its most salient feature is the ability to think abstractly.
The full post here