Bento is a single-portion ..

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Bento is a single-portion takeout or home-packed meal common in Japanese cuisine. A traditional bento holds rice, fish or meat, with pickled or cooked vegetables, usually in a box-shaped container.
A bento lunch is a compact, balanced, visually appealing meal packed in a box. Historically, it’s a Japanese box lunch, similar in concept to the Indian tiffin, the Korean dosirak, or the Filipino baon lunch. In Japanese, “bento” or “obento” refers to the packed meal, and “bento-bako” refers to the bento box itself.
Bento boxes are readily available in many places throughout Japan, including railway stations, and department stores. 
The general rule of thumb for bento make-up is 3 parts carbohydrates such as rice or pasta, 1 part protein, and 2 parts fruits and vegetables, but without candy, junk food or oily foods. Packed this way without gaps, a 600ml box holds a 600 calorie meal, although it’s simple to cut back on carbs for a lighter lunch if you like. It is to ' Think balance ', not only nutritional but also visual. Use a variety of colors and textures in the lunch.
Japanese homemakers often spend time and energy on a carefully prepared lunch box for their spouse, child, or themselves .
Bento can be elaborately arranged in a style called "kyaraben" ("character bento"). Kyaraben are typically decorated to look like popular characters from Japanese cartoons.
In the Taishō period (1912 to 1926), the aluminum bento box became a luxury item because of its ease of cleaning and its silver-like appearance.
A MUST READ STORY ...
By Paul Eide, Sun, May 19, 2013
A 32-year-old man in Kobe, Japan, turned himself in last week for stealing a wallet because he wanted to eat the prison’s food.
When asked why he turned himself in, his response was, “to eat the tasty food Nagata Precinct serves prisoners in its holding cells.”
The boxed meals are called “kamben,” and instead of being prepared in-house are ordered from local bento shops. 
The ingredients are the same as in any other bento in Japan, with meals including grilled salmon, dumplings, eggs, stir-fried veggies, and rice.
What is a Bento Box? Simple "How To" Bento Video
http://www.youtube.com/watch?v=Lovw5uohkCA
http://www.youtube.com/watch?v=md-MsFwTNU0