Microwave Ovens are exciting water molecules at a specific frequency of about 2.5 GHz.
These water molecules in your food are resonating at that high frequency and through the friction among each other heat is created, which actually is so much, that it is actually cooking the food.
The radiation of the microwave oven is said to be well contained within the case and the door with the viewing glass, which is constructed in such a way, that the microwave radiation would not be able to pass through. the holes would therefore have to be smaller in size as the half of the wavelength of the microwave.
Please note very carefully, that even fairly accurate testing equipment and standard exposure levels as are set in Europe are still not seeming to be enough yet, as it has happened to me that I have been testing a home for EMR/EMF and Geopathic Zones and when I got to the kitchen I also tested the Microwave Oven for leakages, as I always do, when the lady of the house told me the following:
While she was pregnant and busy cooking she felt the baby kicking. At first this was not really bothering her, but later she observed more closely and noticed that every time she was in fact walking past the front of the microwave oven the baby was kicking !!!
After she told me that, I checked the microwave oven yet again and even more thoroughly - especially on the door's glass and the rubber seals, but still could find no more deflection of the needle that the width of the needle itself. That is a vary good result, but still too much for the baby !!!
So this shows that the actual regulated radiation levels are not set properly ans should be dropped my a substantial factor still.
Please also see: List of Radiation (affecting all forms of life)