The Incredible Journey of the ButterfliesOrange-and-black wings fill the sky as NOVA charts one of nature's most remarkable phenomena: the epic migration of monarch butterflies across North America. NOVA's filmmakers followed monarchs on the wing throughout their extraordinary odyssey.

To capture a butterfly's point of view, camera operators used a helicopter, ultralight, and hot-air balloon for aerial views along the butterflies' transcontinental route. (Learn more about the production techniques and adventure of traveling with the monarchs in an interview with Director Nick de Pencier.)

The film opens with caterpillars munching milkweed in southern Canada in late summer. Soon each caterpillar transforms itself into a silky chrysalis. Roughly 10 days later, a delicate four-winged monarch emerges.

Then, at some unknown signal, the monarchs take to the air on a two-month, 2,000-mile flight over fields, forests, cities, plains, open water, deserts, and finally mountains to congregate in a tiny, high-altitude region of central Mexico where they've never been before. Incredibly, they arrive by the millions at the same time each year.

Shedding light on this natural wonder are some of the world's leading monarch researchers, including Lincoln Brower of Sweet Briar College, independent biologist Bill Calvert, and Orley "Chip" Taylor of the University of Kansas.

Putting the monarch phenomenon into perspective, Taylor says, "You've got a butterfly that's originating in Toronto, or it's originating in Detroit, Michigan, or it's coming down from St. Paul or maybe even Winnipeg, and it's moving south. Somehow it finds its way to Mexico. Could you do that?"

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