Olive oil was traditionally produced by beating the olives from trees with sticks, soaking them in water, and crushing them in stone or wooden mortarss or beam presses. Nowadays, olives are ground to tiny bits, and the pulp is mixed with water and processed by centrifugation, which separate the oil from other substances.
Olives may be pressed several times, and with each pressing the quality of the oil obtained is less. The oil obtained from the first pressing is called extra virgin. Today olive oil is mainly used in cooking, but has been used for medicines, in cosmetics and soaps, and as a fuel.
The oil was a central product of the Minoan civilization, where it is thought to have represented wealth. The Minoans put the pulp into settling tanks and, when the oil rose to the top, drained the water from the bottom.