If you look across a field in Nigeria, you might see hundreds of midsize trees with green leaves and strange roots being dug up. This tree-looking plant is called cassava. Cassava is the third most important source of calories in the world, behind rice and corn. As many as 800 million people use it as a food source. It may surprise you to find out that most Americans have likely consumed cassava in the form of tapioca! Tapioca is used as a common thickening agent and pudding filler. It's also what is found in the popular "boba tea."