Researchers have developed the first materials that can permanently change from solid to liquid, or vice versa, when exposed to light at room temperature, and remain in the new phase even after the light is removed. The researchers also demonstrated that the light can be used to draw liquid designs in a solid material or solid designs in a liquid material, creating stable materials that are part solid and part liquid. The new materials have potential applications for 3-D printing, molding, and on-demand recycling, among other uses.