Prior to the microwave, stoves and ovens were the primary way food was cooked. This method of cooking food was the norm and was incredibly time consuming. As you will see throughout this website, the microwave was a significant invention that became an important piece of equipment in the kitchen. The microwave continues to be a necessary appliance to this day!
Despite how romanticized the notion sounds, the invention of the Microwave oven was not a stroke of genius with a team of engineers and inventors set out to come up with a faster way of cooking food. Unlike most inventions of the time, the invention of the microwave did not come out of necessity or an eagerness to save time and labor (though that was its benefit!). Rather, the invention of the microwave was largely an accident made by Percy Spencer. The invention of the microwave came directly as a result of the invention of the magnetron.
The magnetron is a tube that uses electrical and magnetic currents to create heat. It was largely unused until Percy Spencer, when working at the Raytheon Corporation, found that it melted a candy bar in his pocket. The next day Spencer arrived to work with popcorn to see what would happen. To his surprise, it popped, and the rest was history! Percy Spencer along with his coworkers at the Raytheon Corporation used this new discovery to invent the first microwave oven.
Putting aside the complete configuration of the microwave (for which the sources are available below, if you really want to know) the most basic explanation of how microwaves work is as follows: Microwaves are divided into two sections, the control section and the high-voltage section.The control section monitors the power of the microwave. It controls the valves which produce the voltage that eventually creates the microwaves. The high-voltage section of the microwave produces extremely high-voltage of about 3000 volts (which is deadly to humans)!! This voltage is converted by the magnetron into microwaves. The microwaves are then dispersed to hit every area within the cooking compartment of the microwave.
(I hope that didn’t make your head spin!)
Put simply, electricity enters the microwave in the form of an electrical current, if all works correctly the control section will pass on the current into the high voltage section. The voltage is then turned into microwaves by the magnetron.
The result = cooked food!
 Shannon Kietzman.. “What is a Magnatron?” http://www.wisegeek.com/what-is-a-magnetron.htm (accessed January 30, 2009).
 Carlton Gallawa, “Who Invented Microwaves? Excerpts from the book The Complete Microwave Oven Service Handbook 2007,” http://www.gallawa.com/microtech/history.html (accessed January 22, 2009).
 Carlton Gallawa, “How Does a Microwave Work?” http://www.gallawa.com/microtech/how_work.html (accessed January 22, 2009).