For them to work efficiently, bees need precise spacing between the frames of the hive's body and the supers. In 1852, American reverend Lorenzo Langstroth (1810-1895) discovered the exact space allowing bees to move between the hive's sections without being tempted to clog everything with propolis. From these data, he created a hive model composed of movable frames in which the bees build the combs. This model, which has since dominated the beekeeping market, allows beekeepers to inspect the colonies and harvest honey without destroying the hives. Bees are essential to the pollination of the lavender fields that cover vast territories on the Valensole plateau and throughout southeastern France.