Holly Lamb, age 7, of Spokane, Wash., for her question:

WHY DOES POPCORN POP?

Of the six different types of corn, the popcorn is probably almost everyone's favorite. It's fun to eat when served plain, with butter and salt, or covered with sugar syrup or caramel.

A tough outer shell covers each kernel. When it is heated, the moisture inside turns to steam. This steam builds up great pressure within the kernel, the pressure bursts the outer shell and the inside of the kernel puffs out.

Other kinds of corn parch or crack when heated, but do not pop. Popcorn grows in Indiana, Ohio, Illinois and Iowa.