A kaleidoscope is an optical instrument, typically a cylinder with mirrors containing loose, colored objects such as beads or pebbles and bits of glass. As the viewer looks into one end, light entering the other end creates a colorful pattern, due to repeated reflection in the mirrors. Coined in 1817 by Scottish inventor David Brewster, "kaleidoscope" is derived from the Ancient Greek ?a??? (kalos), "beautiful, beauty", e?d?? (eidos), "that which is seen: form, shape" and s??p?? (skopeo), "to look to, to examine", hence "observation of beautiful forms." A kaleidoscope is an optical instrument in which bits of glass, held loosely at the end of a rotating tube, are shown in continually changing symmetrical forms by reflection in two or more mirrors set at angles to each other. A kaleidoscope operates on the principle of multiple reflection, where several mirrors are placed at an angle to one another. Typically there are three rectangular mirrors set at 60° to each other so that they form an equilateral triangle, but other angles and configurations are possible. The 60° angle generates an infinite regular grid of duplicate images of the original, with each image having six possible angles and being a mirror image or an unreversed image.