A major development in freshwater pearl farming occurred when Chinese producers began placing bead nuclei deeper within the soft tissues of the mussel rather than in the mantle. This method, commonly referred to as in-body nucleation, produces pearls with distinctly different characteristics from earlier bead-nucleated types.

Early in-body pearls were often baroque and exhibited a rippled surface, but quality has advanced rapidly. Today, fine in-body pearls are large, smooth, and increasingly round. High-quality examples show clean surfaces with no visible blemishes, metallic luster, and intense color with orient.

Kasumigaura pearls are an in-body pearl type and represent the original Japanese expression of this method. Modern Chinese in-body pearls follow the same basic biological approach but are produced at far greater scale and across a broader range of qualities.

In-body bead-nucleated freshwater pearls represent a significant portion of modern freshwater pearl production and are widely available in sizes exceeding twelve millimeters.