Filo is pastry in sheets so thin you can almost see through them. Cooks brush each sheet with oil or melted butter and lay many sheets on top of one another. In the oven the layers dry and lift apart, so the food comes out light and crisp, and it breaks into flakes. A nut-and-honey sweet in many thin layers is the famous example, and many Greek and Middle Eastern pies use it too. You usually buy it ready-made in a packet, and you have to work a little fast so the sheets do not dry out and crack. Though actually, packets often say phyllo, which is the same pastry, just another spelling. And filo is not the puffy pastry Taiwan bakeries often call 酥皮. That pastry rises in thick flakes from butter folded into dough. Filo stays in paper-thin leaves.