Plastic Food Trays in Japan

Hello everyone!

I was wondering, I have seen many plastic food trays at the mall that constitute a complete meal (rice, fish, vegies, etc.). I was wondering whether these are intended to be put in a microwave so as to cook them i.e. is it healthy?

Also, do you know for how long should I cook them?

Any help is appreciated

Do you mean this kind of 'meal'?
https://www.google.co.jp/search?q=%E5%BC%81%E5%BD%93&hl=ja&client=fire...

It is called 'bento' or 'o-bento', basically it is not to be cooked, it's a ready to eat.
They are cooked so that it is good to be eaten without being heat.
Some of the boxes (especially those sold at convenience stores) are OK for microwaved, but some are not.

I recommend just to eat as it is.

Some plastic food trays, for example soled in convenience stores are heat-resisting and intended to be put in a microwave. No problem.
But some plastic food trays, for example sold in supermarkets are not.
Because the former is for takeout,
but the latter is for low-priced meals at home and intended to take to dishes.