Nacre, also known as mother-of-pearl, is a biomineral that forms inside of molluskan shells and also makes up the outer coating of pearls. It is formed through a blend of minerals that are secreted by oysters and other mollusks and deposited inside their shells. The iridescent optical property of nacre has contributed to it being long sought after for decorative purposes, but its fracture-resistant feature also makes it a strong candidate for the creation of biomimetic materials that can be used for, among other purposes, synthetic bone and teeth. Scientists have long studied nacre due to this fascinating combination of characteristics and potential, but the mechanisms behind its formation have remained elusive.