Hot water bottles and pocket warmers are just the thing for Japan's cold winters. Hot water bottles first came to Japan from China in the 16th century. The first pocket warmers are thought to have been devised in Japan as far back as the 12th century. From the age of the shoguns through the Second World War to the present day, the materials and design of hot water bottles have reflected the changing times. Today, hot water bottles and pocket warmers come in all shapes and sizes and are used not only to keep warm, but also to improve blood circulation and relax stiff shoulders. On this edition of BEGIN Japanology, our theme is hot water bottles and pocket warmers. We'll see what these traditional heating devices reveal about Japanese ingenuity.