Our theme week on Accidental Inventions continues today with microwave ovens! The principle behind microwave cooking was discovered by an engineer named Percy Spencer, who was working for defense contractor Raytheon at the time. He was one of the world’s leading experts in radar tube design and was building magnetrons one day, standing in front of an active radar set when he realized the candy bar in his pocket was melting. He decided to investigate further and started experimenting with food. The first food cooked with his microwave oven was popcorn! Raytheon filed a patent for a microwave based on Spencer’s design in 1947. It was 6 feet tall, weighed 750 pounds, and cost around $5000 (over $60,000 today!). Eventually Raytheon acquired Amana, and in 1967 introduced the first popular home model, the countertop Radarange. It still came with a hefty price tag of $495 ($4,000 today!). During the late 1970s, microwave ownership expanded with low-cost countertop models becoming more available. Today, more than 90% of U.S. households own a microwave. Learn more here.