Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to regrow the next year and as a means of asexual reproduction. Two different groups of tubers are: stem tubers, and root tubers.
A tuberous root or storage root, is a modified lateral root, enlarged to function as a storage organ. The enlarged area of the root-tuber, or storage root, can be produced at the end, or middle of a root, or involve the entire root. It is thus different in origin but similar in function and appearance to a stem tuber. Examples of plants with notable tuberous roots include the sweet potato, cassava and Dahlia.