In general there are four types of noodles commonly eaten. Soba noodles, made from buckwheat flour, are thin and gray-brown. Udon noodles come from wheat flour and are very thick and whitish. Ramen, still thought of as Chinese though Japanese consume them voraciously, are medium thickness and gray. Lastly, Somen and Hiyamugi noodles are quite thin and usually eaten cold.
The first three types are eaten as a kind of fast food and even the noodles served in hot soup are usually al dente, and devoured quickly, before they can go limp in the broth.