Japanese know-how and Fourth of July fireworks

This year's Fourth of July was one for the history books. Across the United States, millions gathered to mark a major milestone: the 250th anniversary of the Declaration of Independence. The nation celebrated with parades, barbecues, and spectacular fireworks. Some of the brightest displays that lit up the night sky featured a little Japanese know-how…and NHK World went behind the scenes to find out more.