This book introduces a variety of words related to nature on Earth. A little invisible alien named Little Greenie accidentally lands on Earth and uses his antennas to observe and learn about the planet. Little Greenie discovers that Earth is a beautiful and important place for all living creatures. After ending up in a lonely desert, his people come to rescue him, and he sends a postcard saying, “Happy Earth Day!”

In this book, young readers will learn nature-related vocabulary and interesting facts about Earth along with Little Greenie, the alien.