When the actors were selected to read the letters, it's like an audition for the letter. They want the narrators to take the audience on a trip through history. That's why Yang Yang is the narrator for Huang Jiguang's letter - they are both in their 20s and Yang has military experience.
It's also the first time a full 3-D projection stage has been used to show more than 3,000 video clips used in the series.
Television programs about reading, such as Readers and Letters Alive, started to gain attention in China last year. In Zhu's mind, his new show is about focusing on the historical backgrounds of the stories behind the letters.