Although there is an amount of microwave radiation when the oven is working, which allows food with water or grease to be cooked, the design of microwave ovens ensures that the microwaves are contained within the oven and can only be present when the oven is switched on and the door is shut. For your reference, the amount of radiation that a microwave oven produces is as much as a 40W fluorescent tube, which means there's almost no harm to humans and animals if operates properly.