Every year, millions of Monarch butterflies travel up to 2500 miles to reach a dozen small patches of forest in central Mexico. There, they spend the winter safe from the freezing temperatures in Canada and the midwestern United States. These fragile insects have no idea where they are headed on their migration. Yet, with ingenious navigational systems stored within their eyes, brains and antennae, they locate the same forests and trees that provided sanctuary to their ancestors for generations.