"Once upon a time..." is a children's book that addresses a variety of critical environmental issues. The content is scientifically grounded, yet presented in a way that is understandable for young readers. A wealth of images complements the text, making it easier to grasp the complex topics. This book not only raises awareness of environmental problems but also encourages discussions about sustainable practices. It is ideal for children and teenagers who want to learn in an entertaining way how they can contribute to improving the environment. The combination of engaging illustrations and informative texts makes it a valuable educational tool.