For those who are still wondering....

Tapioca is basically a root starch derived from the cassava, or yuca plant. It's often used to thicken soups and sweeten the flavor of baked goods, and it makes a dandy pudding.
The cassava plant is native to South America and the West Indies, where its thick, fibrous roots are used in a variety of forms: bread flour, laundry starch, an alcoholic brew, and of course, tapioca pudding. As the Encyclopedia Britannica tells us, it was probably first harvested by the Mayans.

Budi Acid Jaya, a tapioca starch producer in Indonesia, uses processed cassava roots to make raw materials for crackers, toothpaste, paper, and textiles. Visit the site for an overview of the starch production process. It involves lots of heat and water.

We suggest you don't try making your own tapioca at home. Cassava roots have traces of cyanide in them! The ever-resourceful Mayans figured out how to extract this poison for their blow darts, leaving the uncontaminated roots free for eating.