Generally speaking, you hope there are very few mysteries about what you're eating for breakfast. But if you're eating Rice Krispies, there is on mystery you might not have the answer to: Why do Rice Krispies snap, crackle, and pop when milk hits the bowl?
The crackling sound coming from your cereal bowl is the result of the walls of each individual piece of cereal fracturing. To illuminate what's going on, the Today I Found Out YouTube channel highlights the two likely explanations for the sound.
Rice is cooked in much the same way popcorn is, forcing it to pop during the cooking process, host Simon Whistler explains. When the rice is done cooking, it forms thin walls around air pockets inside the rice puff. In one possible scenario, the cold milk hits the cereal and causes the air pocket to contract, fracturing the walls of the cereal.
The second theory suggests the cold milk puts a strain on the walls of the cereal, much the same way frozen windshields crack when they're covered in hot water. The shift in temperature causes the walls to snap, crackle, and pop.