Obentou is a portable way to carry a variety of foods. In Japan you can have obentou in two ways. The first way is preparing food in the obentou box at home and the second way is to buying them in places such as a convenient store.
The very first type of obentou was prepared by steaming the rice and then drying it under the sun. The rice usually, was first soaked in water before being eaten. However, the rice was still possible to eat without any water. This type of obentou/rice was carried in a cotton bag and was often carried by soldiers or travelers.
Use of the "お弁当箱" (Obentou box) started in the Adsuchimomoyama period (1568-1603). By the Edo period (1603-1867), there were other types of boxes that allowed you to separate the rice and other foods such as meat, fish and vegetables. Tiered boxes also came out during this time. These tiered boxes and other boxes allowing separation of several foods, are the obentou boxes typically used today.