Microwave ovens are kitchen appliances which are used to cook or reheat food by emitting microwaves. Microwaves are a form of electromagnetic radiation which emit low energy and are generated by magnetrons, found within every microwave oven.
To understand the difference between microwave and conventional heating,lets dig into its scientific details.
Microwaves produced within the microwave oven cause 'dialectric heating' which means that,the heat waves bounce around the inside of the oven and are absorbed by whatever is placed in the oven.
Hence, in order to heat something in a microwave oven, water must be present within the substance. If water is not present, heating will not occur and it would remain cool.
Thus,we may have observed many times that only the upper surface gets heated up while the insides remain cool. Microwaves will excite the food molecules which are already vibrating at very high speeds, creating molecular friction in the water molecules which get vigorously deformed and transfer heat energy across the food molecules which in turn heats them up very quickly.
This is much different than any other method of cooking. Other methods such as convection heating ovens heat up food by transferring heat convectionally from the outside to the inside but the cooking times are much longer along with the addition of oil and extra high temperatures required for cooking a food item( say, for example meat dishes and vegetables).
Thus, the nutritional value will not be significantly affected if you microwave food as compared to the normal cooking process using stoves and ovens, in fact it will preserve more nutrients due to its shorter cooking time.
It is all a misconception being circulated due to the confusion between ionising properties exhibited by radiation, which we are exposed to even while we are using our mobile phones and TV's.
The precautions one can take is to use microwave safe ceramic and glass containers for cooking safely and avoid plastic containers as there may be a risk of the plastic reacting with the food particles over time due to consistent usage.
"If things go wrong, don’t go with them"