The cognitive development of a child is about the construction and development of a mental model of the world. A mental model of a world is really important for humans, because without it we can’t use any information from our past experience, or plan any future actions. In 1936, Jean Piaget was the first psychologist to start the study of the cognitive development. He was the first because he was interested in how a child learn and think. His studies involved children infancy to adolescence, which he also used his three children in his experiment and investigation on the child’s intellectual development. Before Piaget’s studies on the cognitive development, children were consider as less thinkers than adults but proved them that children capability of thinking was more impressive and different from adults. Piaget used two types of methods in his research, such as the Naturalistic observation and the Clinical interview and observation. The Naturalistic observation was more like observing the children in there own habitat without disturbing them, which he used his kids in this method. On the other hand the Clinical interview was meant to observe older children in whom they were able to understand questions and hold conversation. The three basic component of Piaget’s cognitive theory were know as Schemas, the process of adaption that help the transition from one stage to another and the four stages of development such as sensorimotor, preoperational, concrete operational and formal operational. Piaget defines a Schema as the basic building block of intelligent behavior; also know as a set of linked mental representation of the world, which we use it in understanding and responding to situation. When we experiences new thing, new information are stored, which is used to modify, add or change an existing schemas. For example if a young girl have a schema about a type of animal, such as a cat. According to her schema, cats are furry