Cultured pearls are humanity’s work at duplicating what nature first started. A ‘seed’ or ‘nucleus’ (typically a round bead made of mother of pearl) is inserted into the oyster and the oyster is returned to the sea. The oyster will coat this ‘seed’ with nacre to create a cultured pearl. Freshwater pearls are also cultured. Multiple tissue seeds are inserted into a freshwater mussel. The mussel coats these seeds with nacre to produce cultured freshwater pearls.