Preschool to early elementary school children (ages 4–8).
(English: “The Structure of My Body with Mama: The Differences Between Boys’ and Girls’ Bodies I Learned by Asking Mom ‘Hey, Hey’” ) Informative Write-Up Title: Mama to Boku no Karada no Shikumi Author/Illustrator: Typically credited to Shuntaro Tanikawa (poet/lyricist) and Yoko Imoto (illustrator), though several similar titles exist under the “Kagaku no Tom” (Science Friend) or “Gakken” educational series. Mama to Boku no Karada no Shikumi Okaa-san ni C...
Based on this phrasing, you are most likely referring to the well-known Japanese educational children’s book: Preschool to early elementary school children (ages 4–8)