Orange-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. 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.