What does it do to my food?
All microwaves have a magnetron that generates micro-waves that radiate in a electromagnetic field. These waves bounce off the surface of the oven, produce heat and get absorbed by anything that's in the oven. That's how your food gets heated or cooked. The heating in uneven because the parts of food that have the highest water content absorb the highest amount of heat and typically, the heating begins from outer layers.
Some nutrients like Vitamin C break down when heated. So while it is a microwave or gas burner, heating is taking away vitamin C away from your food though in a microwave, the duration of heating is lesser. But research also says that the waves in a microwave change the molecular structure of the food, making it 'dead' or nutritionally deficient. It was found that microwave heating affects Vitamin B12 in particular, which is important for our and red blood cells, rendering it inactive.
Not just this, breast milk, if heated in microwave can grow 18 times as many E coli bacteria as non microwaved mild. Microwaving eggs with their shell on is also extremely dangerous as the pressure inside the egg can make it explode, much later after the egg has been taken out if the oven.
A Swiss study indicated that microwaving and eating vegetables can significantly decrease the red blood cell count in your body and increase cholesterol.
When you heat food in plastic containers in a microwave according to research at Harvard medical school, the phthalates in the plastic leak into the food which can be extremely damaging for the body as it can create carcinogens. Heating food in plastic cling wraps or in plastic take-out boxes should definitely be avoided.