Hyewon Yum is the author and illustrator of many books for children, including Toto, The Twins' Blanket, Saturday is Swimming Day, Grandpa Across the Ocean, and Mom, It's My First Day of Kindergarten!, which received the Ezra Jack Keats New Illustrator Award. She is also the illustrator of Maya Myers’s Not Little and Not Perfect and Andrea Wang’s Luli and the Language of Tea. Born and raised in Seoul, South Korea, she now lives in Brooklyn with her family.