One of the best works and the biggest reason why Sejong was called great was because he created the Hoon min jung um (訓民正音). It is called in modern days as 'Han-gul (한글)'. Because of the creation of the Hoon min jung um, Joseon (now Korea) now got its own alphabet, and many people, most of whom have never learned how to read Hanja (Chinese characters used for Korean) could learn how to read and write much more easily than before.