Consider the humble "donburi." These oversized rice bowls filled with rice and topped with simmered fish, meat, vegetables and/or stewed goodies smothered in a sweet sauce, are one of the basic fuels that keep Japan running. Donburi is such a major part of the Japanese diet that it may be surprising that it is such a recent phenomenon, and one of Japan's original convenience foods. The dishes first appeared shortly after the Meiji Restoration in 1868, when urban life took on a modern bustle and time suddenly got a bit too tight for the leisurely lunches the Japanese were used to, and people needed something they could eat on the run that would stick to their ribs.

More recently chains of donburi shops have been sprouting up all over the country, catering to the hungry hordes that spill out of office buildings at lunch time. Every region, indeed every city and town of any size in Japan has its own specialty version of the dish. The sauce varies with the season, ingredients, and region, typically consisting of a "dashi" soup stock flavored with soy sauce and sweet "mirin" syrup.

The most popular donburi are "katsudon" (breaded "tonkatsu," or fried pork, cutlet with onion and egg) and "tendon" (tempura shrimp and vegetables). Following close on their heels in popularity are "oyakodon" ("parent and child" -- chicken and egg), and "gyudon" (beef and onion), a cheap, delicious and extremely popular dish nationwide. A chain of gyudon restaurants, Yoshinoya, has hundreds of outlets in Japan, and a good foothold in the U.S. and elsewhere as well. Some other favorites are "una-don" (broiled unagi eel with a sweet brown glaze of soy sauce and sweet sake on it, and usually sprinkled with "sansho" pepper) which is a midsummer treat, possibly because that's when the eel are running, but also, I've been told by unadon aficionados, because the oil in the eel helps fortify the eater against the heat. At any rate, smoke from a charcoal eel barbecue billows from an unagi joint on every block of every shopping street in every neighborhood in Japan -- another distinctive fragrance of summer in Japan.

The variety of donburi is endless. "Chukadon" is Chinese-style donburi, with Chinese stir-fried vegetables, seafood and meat in a thick Chinese-style sauce. "Tekkadon" has a topping of raw tuna with strips of nori (seaweed) and sometimes ground "yamaimo," a kind of gooey mountain potato. "Maguro-don" has tuna sashimi, and "ikura-don" has salmon roe (ikura) garnished with some "shiso" leaves.

Most of these go well with some clear soup and pickles, which is what you get if you order the "donburi setto" at a restaurant, and some green tea, which is usually all-you-can-drink.

Naturally, this simple meal lends itself well to innovation. Restaurant workers at the end of a shift often chow down on leftover goodies over rice, a meal known as "makanai-don" (employee-bowl). And every harried Japanese mother looking for a quick and nutritious lunch for her kids serves up stewed leftovers on rice for lunch several times a week.

Incidentally, one never, eats plain rice out of a donburi bowl - it looks like gluttony.