Bento is a wooden or plastic box with several compartments to hold different food, traditionally rice, sushi, vegetables and pickles, but also sweets and fruits. In Japan they are prepared for office, school or pic-nic and girlfriends often prepare them for their male partners.
You can see here few creations (even a 'acid' one)
by the talented 'bento artist' Sakurako Kitsa and many more on her Flickr page and here.
Other bento compositions (not Kitsa's) here