The behind-the-scenes tales of hit products and creations from Japan: this is Japan's Top Inventions. This time, durable timepieces that don't break when dropped: shock resistant wristwatches. These unique watches were created by a Japanese firm in 1983, and are now available in 138 countries and regions. Over 100 million units have been shipped to date. Discover their surprising inspiration -- a child playing with a rubber ball in a park -- and more in the little-known story behind this invention.