When you slice open a watermelon, you'll find sweet, juicy red or pink flesh filled with black seeds, all protected by a thick green rind. Watermelons are one of summer's most refreshing treats, made up of about 92% water, which makes them perfect for hot days when you need to cool down.

Watermelons are actually berries, though they're so large that most people think of them as something different. They grow on vines that spread across the ground, and a single watermelon can weigh anywhere from 10 to 50 pounds or more. Farmers around the world have been growing watermelons for thousands of years, originally cultivating them in Africa before they spread to other continents.

When you're shopping for a good watermelon, people often tap on it and listen. A hollow, deep sound usually means it's ripe and ready to eat. The rind, while not usually eaten, is technically edible, and some people even pickle it.