Through studies to clarify the cellular origin of lens regeneration in the newt, the pigmented epithelial cells of the iris and the retina of many vertebrate species have been shown to possess a dormant potency to transdifferentiate into the lens. The method of in-vitro culture of pigmented epithelial cells has been optimized to enable detailed studies of the transdifferentiation process by molecular techniques. Growth factors and extracellular matrix components are found to be important in the control of the transdifferentiation process. New systems for in-vitro culture are introduced, while prospects for renewed in-vivo studies using newts are given.