Our eyes help us look at the world, but there are many things we cannot see. Atoms are the building blocks of everything in the universe, from planets and stars to the cells that make up plants, animals, and the human body. Atoms are invisible because they are so small, but bigger things can be invisible, too. Ancient artifacts and buried bones are hidden under the ground, while invisible forces such as earthquakes and winds shape life on Earth. This book explores the invisible world inside different animals. Find out how animals are made up of a complex network of microscopic cells. See how cells divide so animals can grow and reproduce. Learn about the tiny pests and parasites that make animals ill. Book jacket.