NOVA: The Incredible Journey of the Butterflies Blu-ray

Every year, 100 million monarch butterflies set off on an incredible journey across North America. These beautiful creatures fly 2,000 miles to reach their remote destination: a tiny area high in the mountains of Mexico. Yet scientists are still puzzling over how the butterflies achieve this tremendous feat of enduranceand how, year after year, the monarchs navigate with such hairs-breadth precision.