The combination of Mentos and Diet Coke creates a well-known and dramatic reaction. When a Mentos candy is dropped into a bottle of Diet Coke, it causes a rapid release of carbon dioxide gas. This reaction occurs because the surface of the Mentos is covered in tiny pits, which provide nucleation sites for the gas bubbles to form quickly. This explosive effect is often used in science experiments and viral videos. The reaction is not as intense with regular Coke due to its higher sugar content, which affects the gas release. The phenomenon is a fun demonstration of chemistry in action.