Piaget was not really interested into the knowledge having by the children but he was more fascinated by the way of children think, observe their surrounding and how they express it into speeches (Krause et al., 2007).As example, instead of sucking thumb, infants will replace it with their toys.They may squeeze their rubber toys, when it goes "mooo mooo", they will get excited and squeeze it again.Brenda (2010) mentioned in this sub-stage, the infants will be doing the same actions but it extends out to the environment such as replacing sucking their thumbs with rubber toys.In other words the infants are having improvement in their reactions.For example, infants will show happy expression or laughing when we are teasing and cuddling with them, this shows that infants started to make sense things around them but with limited abilities because it is only based on what they get through their senses.In sensorimotor, there are sub-stages that divided into 6 categories, that are reflexes, primary circular reactions, secondary circular reactions, coordination of reactions, tertiary circular reactions and early representional thought (Brenda, 2010). Piaget’s Theory of Cognitive : apply to child development. Piaget’s Theory of Cognitive : apply to preschool children. Children started to develop their understanding through their surrounding based on four stages of cognitive development. In addition, Gartrell (2011) also stated that Piaget’s method by questioning the children is called as clinical method.The first sub-stage is reflexes, according to Brenda (2010) this sub-stage is occured from the birth of the infants until 1 month old.During this stage, infants understand their surrounding by using simple reflexes for example they will starting to smile.