Sweet potato vermicelli is similar in texture to bean thread vermicelli, and turn transparent or glass-like when cooked - hence the name glass or cellopane noodles. They are most widely used in Korean japchae - vegetables stir-fried with sweet potato vermicelli. Sweet potatoes were brought to Japan in the 17th century, and then on to Korea in the mid-18th century to help alleviate famine. It has been a significant part of the diet in both countries since.