Question: Why does popcorn pop?

James Verdon answered on 28 Jun 2012:

Popcorn consists of a corn not unlike sweetcorn, but with a harder outer shell, with starchy material and oils inside. When you heat popcorn, the oils inside the corn start to heat, forming superheated pressurised steam inside the shell. Initially, the hard outer layer withstands this, but eventually the pressure becomes to great and the shell explodes. When the shell explodes, the steam suddenly expands in volume, and this puffs up the starchy internal material into the puffy white foam that is popcorn.

Plain popcorn is actually a very healthy snack. But often at cinemas it is loaded with salt and oil, making it a lot less healthy.