In this video segment adapted from NOVA, watch residents of the Peruvian Andes build a suspension bridge made entirely of grass. The ancient Inca were a textile society and thus skilled in working with natural fibers including alpaca and cotton. Still, it might surprise people today that their solution to crossing the canyons and gorges of their mountainous empire featured another fibrous material: grass. When you consider how they built a simple suspension bridge, you'll realize that not only was this a practical solution, it was also a safe one. In this video segment adapted from NOVA, watch residents of the Peruvian Andes as they build a traditional and functioning grass bridge the likes of which enabled the ancient Inca people to flourish for several hundred years. Grades 3-12.

This video segment, adapted from NOVA, traces the evolving history of theories about gravity and a force that may oppose it, along with our understanding of the impact of both of these forces on our expanding universe.

In this video segment from NOVA scienceNOW, learn about the effects of gravity as astrophysicist Neil deGrasse Tyson falls through a virtual hole through Earth's center.

In this video segment adapted from NOVA, a meteorologist explains how an unusual weather pattern led to one of the most devastating floods of this century.

In the Great Job! video series, real professionals give middle and high school students a behind-the-scenes look at their exciting careers.

The newest videos in the series highlight: a Biomedical Engineer, Radiologist, Machinist, Prosthetic Specialist, and a Sonographer.

Learn about a study in which participants discovered contaminants in their homes, and how green chemistry may provide alternatives to such everyday toxins, in this video adapted from Contaminated Without Consent.

Using the green screen video technique your classroom opens up a world of possibilities. These easy tips demonstrate how the technique can be used for student newscasts, artistic performances, even action adventure videos!

Metals are grouped according to their characteristics. This video segment uses the periodic table for an in-depth discussion.

This collection of six images captures the magnificence of human development -- the transformation from baby to woman.

This video segment explores how one marine biologist used the scientific process to discover how whales hear.

Guinea Bissau Conflict. Program examines the guerilla warfare underway in the African country of Guinea Bissau as part of the campaign for independence being waged in that country. Program is divided into two segments: the first consisting of an on-location British film about Guinea Bissau guerilla troop B-30 as it proceeds to an attack site, the second of an interview with Party for the Independence of Guinea and Cape Verde (PAIGC) representative Gil Fernandes, who discusses his work, background, and the state of the war. Film contains commentary by PAIGC founder Amilcar Cabral. Produced by John Slade. Directed by Russell Tillman.

In this video adapted from Bullfrog Films, GwichŰ__Ű__ŒŒÇin Chief Evon Peter of Arctic Village, Alaska, describes his people's connection to the caribou and their passion to protect Alaska Native land and traditions.

Although repeatedly exposed to HIV, Steve Crohn's blood cells were never infected. Dr. David Ho investigates in this video segment from NOVA: "Surviving AIDS."

In this video segment from Cyberchase, the CyberSquad determines the fairness of a game in which there are three shapes distributed equally on nine squares.

In this video segment from Religion & Ethics Newsweekly, meet an American Muslim as he prepares for Hajj, the pilgrimage to the holy city of Mecca that commemorates the Abrahamic roots of Islam.

Performed with over two million other Muslims, the rites of Hajj, the required pilgrimage to Mecca, have a profound personal impact on each pilgrim. In this video from Religion & Ethics Newsweekly, a Muslim from America experiences Hajj for the first time.

Students learn about an American Muslim's impressions of his first pilgrimage to Mecca in this video segment from Religion & Ethics Newsweekly.

A dining hall at Dartmouth College accommodates the religious dietary requirements of Muslims, Jews and Hindus as explained in this video from Religion & Ethics Newsweekly.

In this ZOOM video segment, join Hana as she learns traditional Japanese drumming with her Taiko group.

Follow along as artist Sirron Norris demonstrates how to draw various emotions on cartoon faces. See how subtle changes make a big difference when expressing emotion through art.