The Heian period of Japanese history lasted from 794 to 1185 CE. Sei Shōnagon lived and died during this time. Not a lot is known about her as a child. We only know about her personality by her writing, especially "The Pillow Book". This book contains a lot about her life at the imperial court and her feelings. It is a collection of lists, poetry, gossip and observations from her years in the court (things she saw and how she felt about them). "The Pillow Book" became very well-known during the Heian period. It revealed an interesting view on life at court.