The concrete operational stage is the third stage of cognitive development stage proposed by Piaget. At this stage, the children show the logical thinking that is related to the conservation principle. They start to think that things are not changing, yet to be changed their physical appearance.
For example, the quantity of water will be the same whether the container size would exchange. But the quantity of water will be the same. The children who do not develop conservation they still are confused in long container quantity and wide container quantity.
