Korea's education that encourages children to live based on the thoughts and judgement of other people, rather than cultivating individual thoughts and stressing one's own values, often leads to inability to distinguish what is right from wrong after losing one's voice, his or her own thoughts and values. We all have our own 'eye' (insights). In this context, it refers to an 'internal eye,' instead of a body part. Thus, we should understand the characteristics of our own internal, individual development. Generally, the development stages of each child vary in terms of pace and outcomes. Therefore, identical development of different children is nearly impossible. However, many parents and teachers tend to generate limited, superficial assessment on the developmental characteristics according to age, overlooking the internal development (feelings and emotions), a critical component to thrive in today's society. If the internal development is not understood, children who go beyond the age-based generalized characteristics are labeled as a 'problem child' and a misleading approach is adopted. Therefore, methodological approach should be used only after understanding the internal developmental stages of children. Thus, the primary purpose of this study is to help understand the development of children by observing how they play and exploring the importance of play and toys in order to understand the internal developmental stages of children. Furthermore, this study is aimed at providing basic guidance on play-based education between parents and children and stressing the importance of internal development of children, through related theories and exploration of toys and play.