The definitions of constructivism are very simple but for a better understanding of constructivism, we need to know different aspects of constructivism.Personal constructivism can be summed up by the following statement of Jean Piaget‘Knowledge is actively constructed by the learner, not passively received from the environment. Radical constructivism adds the second principle to trivial constructivism, which can be expressed as: ‘Coming to know is a process of dynamic adaptation towards viable interpretations of experience. The knower does not necessarily construct knowledge of a real world.’ These principles of personal constructivism and radical constructivism are actually the two basic principles of constructivism, according to Baber and Allen. They are:‘The function of cognition organizes the experiential world rather than seeks to discover ontological reality’. These two principles are part of a broad system for the development of cognitive abilities.Piaget ‘inspired a vision of children as busy, motivated explorers whose thinking develops as they act on the environment.’ This development takes place as the children move through four stages between infancy and adolescence.In other words, there are four primary cognitive structures (i.e., development stages) according to Piaget: sensorimotor, pre-operations, concrete operations, and formal operations.