Opal displays a burst of striking colors known as play of color. As the stone is moved, the appearance changes and a different display of rainbow-like colors can be seen from different angles. This play-of-color is caused by the diffraction of light hitting the stone. In the 1960s, intensive microscopes magnifying between 20,000x and 40,000x revealed that tiny silica spheres (150 to 300 nanometers) with water interspersed make up opals. The shape, size, and alignment of these spheres affect the color of the opal.