A pearl does not begin as something precious. It begins as a problem. Inside an oyster, a tiny particle slips in and settles where it does not belong. It might be a parasite, a rough fragment, or ...

For at least 164,000 years, oysters have been part of the human diet, but people have been finding pearls in oysters for much longer — as early as 2300 BC when Chinese royalty received them as gifts.

For centuries, researchers have puzzled over how oysters grow stunningly symmetrical, perfectly round pearls around irregularly shaped grains of sand or bits of debris. Now a team has shown that ...