The method and principle are as follows:

1. Put a proper amount of rice into the popcorn pot, seal the lid, and then put the popcorn pot on the stove and rotate it continuously to make it evenly heated, so that delicious popcorn can be popped.

2. During the heating process, the temperature in the pot keeps rising, and the pressure of the gas in the pot also keeps increasing. When the temperature rises to a certain extent, the rice grains will gradually soften and most of the water in the rice grains will turn into steam.

3. Due to high temperature and high pressure of water vapor, the softened rice grains expand. But at this time, the pressure inside and outside the rice grain is balanced, so the rice grain will not explode in the pot.

4. When the pressure in the pot rises to 4-5 atmospheres, the top cover of the popcorn pot suddenly opens, the gas in the pot expands rapidly, and the pressure drops rapidly, which increases the pressure difference between the inside and outside of the rice grains, resulting in the rapid expansion of high-pressure steam in the rice grains, which instantly explodes the rice grains into popcorn.