This video segment describes the basics of the circulatory system: how the heart pumps the blood that carries oxygen and nutrients throughout the body.

This video segment adapted from NOVA scienceNOW shows how the common wood frog freezes solid every winter, an adaptation that allows the organism to survive the cold winter.

In this video segment adapted from NOVA scienceNOW, hydrogen fuel cell cars promise pollution-free driving, but will we see them anytime soon?

In this video segment adapted from FETCH!, contestants are challenged to use materials from a garbage dump to build a boat that floats, can be steered, and is propelled by something other than oars.

Just after World War II, nuclear scientists turned their attention from fission to fusion. This video segment adapted from AMERICAN EXPERIENCE looks at the beginnings of thermonuclear power generation.

This video segment adapted from NOVA shows how Galileo, using his newly developed refracting telescope, observed four of Jupiter's moons, the first astronomical bodies to be discovered since ancient times.

Einstein called Galileo the "father of modern physics." This media-rich essay from the NOVA Web site looks at Galileo's quest to understand the mathematics of motion.

In the early 1600s, most people believed that the Sun revolved around a stationary Earth. This video segment adapted from NOVA tells how Galileo proved that the Sun, not Earth, is at the center of our universe.

This video segment adapted from NOVA shows how Galileo used his telescope to carefully observe and study sunspots.

Scientists don't always get it right. This video segment adapted from NOVA looks at Galileo's failed theory for the motion of the tides.

This video segment from the Secret of Life School Video: "On the Brink: Portraits of Modern Science" explores the genetics of breast cancer.

The shared set of genes for body segments, possessed by all animals, are discussed in this video segment from Evolution: "Great Transformations."

In this video profile adapted from NOVA scienceNOW, learn about geneticist and rock musician Pardis Sabeti, whose innovative insights into natural selection demonstrated how beneficial mutations spread quickly through a population.

This list from NOVA: "Cracking the Code of Life" Web site provides some of the basic, yet impressive, facts and figures about the Human Genome Project.

This video segment from NatureScene examines the landforms of Death Valley and how they came to be.

See how the geology of the North Dakota badlands has changed over time in this video segment from NatureScene, featuring the landscape at Theodore Roosevelt National Park.

This ZOOMSci video segment teaches you how to germinate seeds in a plastic bag and helps you understand some of the factors that influence the germination process.

Learn how scientists regulate a nuclear reactor in this animation-enhanced essay from the FRONTLINE Web site.

This video segment, adapted from NOVA, chronicles the education of leading chemist Percy Julian. Although Julian began his elementary school years in the Deep South under Jim Crow laws, he became one of the few African Americans of his time to earn a Ph.D.

In this video from Nature, learn about the many different features and effects of glaciers in Ireland.