the number of ramen vendors: private companies even rented out yatai starter kits consisting of noodles, toppings, bowls, and chopsticks. Ramen provided a rare opportunity for small-scale postwar entrepreneurship. The Americans also aggressively advertised the nutritional benefits of wheat and animal protein. The combination of these factors caused wheat noodles to gain prominence in Japan's rice-based culture. Gradually, ramen became associated with urban life. Modern period In 1958, instant noodles were invented by Momofuku Ando, the Taiwanese-Japanese founder and chairman of Nissin Foods. Named the greatest Japanese invention of the 20th century in a Japanese poll, instant ramen allowed anyone to make an approximation of this dish simply by adding boiling water. Beginning in the 1980s, ramen became a Japanese cultural icon and was studied around the world. At the same time, local varieties of ramen were hitting the national market and could even be ordered by their regional names. A ramen museum opened in Yokohama in 1994. Today ramen is one of Japan's most popular foods, with Tokyo alone containing around 5,000 ramen shops, and more than 24,000 ramen shops across Japan. Tsuta, a ramen restaurant in Tokyo's Sugamo district, received a Michelin star in December 2015. Types A wide variety of ramen exists in Japan, with geographical and vendor-specific differences even in varieties that share the same name. Although ramen usually has toppings, ramen can be broadly categorized by its two main ingredients: noodles and broth. Noodles Most noodles are made from four basic ingredients: wheat flour, salt, water, and , derived from the Chinese (), a type of alkaline mineral water containing sodium carbonate and usually potassium carbonate, as well as sometimes a small amount of phosphoric acid. Although ramen noodles and Udon noodles are both made with wheat and are similar, they are different kinds of noodle. The is the distinguishing ingredient in ramen noodles, and originated in Inner Mongolia, where some lakes contain large amounts of these minerals and whose water is said to be perfect for making these noodles. Making noodles with lends them a yellowish hue as well as a firm texture. Eggs may also be substituted for . Some noodles are made with neither eggs nor and should only be used for yakisoba, as they have a weaker structure and are more prone to soaking up moisture and becoming extremely soft when served in soup. Ramen comes in various shapes and lengths.