Sea stars were the basis of Dr. Robert Pain's groundbreaking experiment to explore his theory of keystone species. Who'd have thought that an insignificant tidal pool invertebrate could have such an impact on its environment? This book breaks down the concept of keystone species and sea stars' role in their habitat for young readers. Beautiful full color photos bring the world of the tidal pool to life. Fascinating fact boxes break down important ideas. Age-appropriate vocabulary and a glossary make learning enjoyable.