Todd Bolen/

FLOUR MILLS. Stone mills were used to grind grain into flour. This was done both at bakeries in cities and at home—in smaller quantities with more primitive tools. The above mill stands outside a bakery with an oven at the Roman site of Pompeii, which was destroyed by an eruption from Mt. Vesuvius in 79 C.E. The mill consists of a hollow top stone and a solid, stationary bottom stone. Wooden beams, fitted into slots in the top stone, were used to turn the mill. Ancient Romans would have poured grain into the top stone and then rotated it to crush the grain between it and the bottom stone. The end result was flour.