Chinampa can be described as rectangular enclosures filled with mud and decaying matter rising above the surface of the water. Another achievement that the Aztecs were famous for is the discovery of popcorn, chewing gum, and chocolate. Corn was the staple of the Aztec diet and was used to make tortillas and used for ornaments on the headdresses of nobility and priests. Chewing gum was also discovered by the Aztecs; it came from the sap of the sapodilla tree and was called "chicle" in Aztec society. Along with popcorn and chewing gum, chocolate was used by the Aztecs. Chocolate was considered very expensive and considered a luxury and also often used as currency, it was commonly used in sacrificial events and reserved for the noble classes. Cacahuatl was an early form of chocolate drink by the Aztecs