The "Makunouchi Bento"Originated in the Edo Period
There are several theories about the origin of the "makunouchi bento." The two most likely ones are as follows: (1) the "bento" eaten between the acts of a play (the word "makunouchi" means "in between curtains") by the audience, and (2) the "makunouch-rikishi" (the top sumo wrestlers) ate this "bento." The "makunouchi bento" is said to have originated in the middle of Edo period (around the 18th century). This kind of "bento" started being sold at train stations as "ekiben" since the Meiji era (1868-1912), when it became popular.
The "makunouchi bento" is generally a set of white rice with assorted dishes. Only found in Japan, it is arranged so beautifully that it is popular among foreign tourists.
In the computer world, it is a well-known story that Apple Corporation proposed the "bento" format of "OpenDoc" in 1993. The concept behind the format is derived from the Japanese "bento," which consists of assorted dishes in a box.