Aerial view of the Messolonghi salt pans, Greece. Salt, sodium chloride, has played a crucial role in the history of civilization and in ancient Greece it was used as a commodity for trading slaves. It is said that the expression 'not worth his salt' came from this practice. Salt was also used during sacrifices and religious rituals. The Messolonghi Aetoliko lagoon system is considered to be one of the most important Mediterranean salt lagoons and is certainly the largest in Greece, producing 60 percent of the country's salt. A basic advantage of natural sea salt, as opposed to its mineral form, is its crystalline structure, which contains trace elements of marine water, such as potassium, calcium, magnesium, etc. During sea water evaporation, condensation, there is a successive, natural crystallisation of these mineral salts which is reflected by the various colors visible from the air.