Electrodes from a power supply are attached to the transparent electrodes. With no applied voltage, This results in the translucent, "milky white" appearance. When a voltage is applied to the electrodes, allowing light to pass through the droplets with very little scattering and resulting in a transparent state.
In suspended-particle devices (SPDs), a thin film laminate of rod-like nano-scale particles is suspended in a liquid and placed between two pieces of glass or plastic, or attached to one layer. When no voltage is applied, the suspended particles are randomly organized, thus blocking and absorbing light.
When a voltage is applied, it becomes transparent, and when the voltage is reversed, it changes like a mirror and is reflected.