Puffed cereal refers to cereals like wheat, millet , corn or rice which are made by exploding cooked cereal from a pressure chamber, thus expanding the grain to several times its original size. The principle of the puffing process is heating the cereal, and sometimes other vegetable products, in a pressure chamber in presence of steam. When the containment vessel's seal is suddenly broken, the entrained steam then flashes and bloats the endosperm of the kernel, increasing its volume to many times its original size. Puffed cereal includes ancient puffed grains like popcorn as well as puffed rice. Puffed cereal is used in snack foods and breakfast cereals, and is also a popular street food in some parts of the world. Puffed cereal like puffed rice is an ingredient of bhel puri, a popular Indian chaat item. It is also used in temples and gurdwaras as prasad.