Angel food cakes use no fat at all and no chemical leaveners; they rely only on whipped egg whites that have been stabilized with cream of tartar to give the cake its volume. Sponge cakes typically use butter for the fat, and it is creamed into the sugar. Eggs are added either whole or separated with the whites whipped into stiff peaks and folded into the cake batter. Chiffon cakes set themselves apart by using vegetable oil as the fat source. To get high volume, eggs are separated and the whites are whipped to stiff peaks and folded into the batter.