Dear chang yeong sil,

    Hello? My name is Jin U. You don't know about me but i know you. I know a lot about you. I'll review what you did for us.

    When you were young, you knew a lot of thing. You had brave, smart, and never ending enthusiastic mind. I think your mind made you to became a scientist. King Se jong helped you to became a scientist ,too. You invited a lot of helpful invention by king Se jong's order.

    Sun clock, water clock(Ja gyeong nu), and science books were the examples of your invention. They were so helpful to modern people and scientists.Thank you to invented helpful inventions!