The ink is electrophoretic, meaning that it contains charged particles that can be moved around by electricity. These are microparticles made of polyethylene and either titanium dioxide, which is white, or an inorganic black pigment. The white ones are negatively charged, while the black ones are positively charged. Then, black and white microparticles move towards the negative and positive regions, and an image is formed by the particles at the top of the display.