Starch is a substance obtained from tubers, roots and piths of some plants. The best known is potato starch, extracted from both the common potato and the sweet potato. Then there is the tapioca, obtained from the root of cassava and the sago, which instead comes from the pith of palms.
Starch is presented in the form of a very fine and impalpable white powder. It has binding and thickening properties, for this reason it is often used instead of flour in the preparation of creams and sauces, soft doughs (such as Margherita pasta) and crumbly biscuits.