Introduces the planet Mars, exploring its atmosphere, composition, and other characteristics and looking particularly at how humans learned about the only planet that can be seen clearly from Earth.

Explores the science of seasons, focusing on winter, discussing freezing and melting, the causes of cold weather, life in winter, and other topics; and includes a glossary, references, an index, and photographs.

Describes the various parts of the human circulatory system and explains how and why blood is circulated throughout the body.

Introduces the planet Neptune, exploring its atmosphere, composition, and other characteristics and looking particularly at how humans learned about the gas giant that is four times the size of Earth.

Explores the science of seasons, focusing on spring, discussing signs of spring, the changes that occur, spring planting, and other topics; and includes a glossary, references, an index, and photographs.

Explores the land, people, history, economy, and travel opportunities of Puerto Rico.

Introduces the sun, exploring its atmosphere, composition, and other characteristics and looking particularly at how humans learned about the star at the center of our solar system.

Learn about the forces shaping the world's crust.