This video segment from NOVA: "The Mystery of Animal Pathfinders" explores how the migratory patterns of shorebirds have evolved to coincide with the spawning of horseshoe crabs.

In an interview, a zookeeper at the Columbus, Ohio, polar bear exhibit describes time she spent at Churchill, Manitoba, educating tourists about polar bears and what can be done to help populations in the wild. This interview appeared in the free, online magazine Beyond Penguins and Polar Bears.

This video segment adapted from Discovering Women profiles Fermilab physicist and Harvard professor Melissa Franklin.

All animals develop and grow over time. The animals in this video segment, however, undergo very dramatic changes on their way to adulthood -- a developmental process known as metamorphosis.

In this video from DragonflyTV, Tiana and Sammy measure, record, and analyze the results of a drop box test to find out how everyday items behave in microgravity.

This video segment from NOVA: "The Mystery of Animal Pathfinders" explores the migratorial exploits of monarch butterflies.

In this interactive activity from ChemThink, learn about covalent molecules and how the VSEPR theory predicts the shapes of covalently-bonded molecules.

This video segment follows neurophysiologist Allen Counter as he studies an epidemic of hearing loss in Moriussaq, Greenland, one of the quietest places on Earth. Footage from NOVA: "Mystery of the Senses: Hearing."

This video segment adapted from NOVA relates the dramatic story of vulcanologists trying to predict the timing of the cataclysmic eruption of Mount Pinatubo in the Philippines.

This interactive activity adapted from A Science Odyssey Web site helps you visualize different types of plate tectonic activity and shows the impact this activity has on Earth's surface.

Join a group of middle-school students on a visit to a laboratory at the Massachusetts Institute of Technology, where they experiment with "mystery mud" and learn about the relationships between magnetism, particle motion, and changes in the state of matter.

In this video segment adapted from NOVA, NASA learns hard lessons from the first American attempt to do work while "walking" in space. The video also explores Newton's third law of motion.

This video segment adapted from the NOW-RAMP 2002 Expedition documents a research expedition to Nihoa Island. It showcases Nihoa's unique birds and plants, the threat posed by invading grasshoppers, and restoration efforts.

Nitrogen, one of the most abundant elements in the universe, is essential to life. This interactive activity adapted from the University of Alberta provides an overview of the nitrogen cycle.

This video segment adapted from FRONTLINE looks at nuclear fission as an energy source that can be used to generate electricity.

This video segment produced for Teachers' Domain features a time-lapse video of clouds forming, changing, and moving across the sky.

This brief video segment produced for Teachers' Domain features time-lapse video of a sunrise and a sunset.

This video segment adapted from Shedding Light on Science illustrates how light changes speed, and thus direction, in a process known as refraction.

This video adapted from KTOO explores the impact of oil contamination on the herring population of Prince William Sound, Alaska, in 1999, 10 years after the Exxon Valdez oil spill.

This video segment adapted from NOVA follows the clean-up effort after the 1989 Exxon Valdez oil spill off the coast of Alaska. Also featured is a marsh where an oil spill occurred 20 years earlier; analysis suggests that environmental damage may last for decades.