Although ramen is a Japanese icon, its roots are Chinese. The word 'ramen' is the Japanese transcription of the Chinese 'lamian' (pulled noodles). The dish was introduced to Japan by Chinese immigrants in the late 19th or early 20th century. The first specialized ramen shop, Rai-Rai Ken, opened in Tokyo in 1910. The key difference in ramen noodles is the use of 'kansui'—an alkaline mineral water containing sodium carbonate and potassium carbonate. This alkaline solution gives the noodles their yellow color, firm texture, and prevents them from disintegrating in the hot broth. Ramen didn't become a national sensation until after WWII, when wheat flour was cheap and plentiful in Japan.