 Quantum dots are small, semi-conducting nanocrystals that can be made up of a variety of different elements such as silicon, cadmium selenide, or cadmium sulfide. They range in size from 2 to 10 nanometers. One nanometer is about the width of two silicon atoms. These semi-conducting materials are able to absorb light. When they release that energy, they transform it into a different color of light. The specific color that a quantum dot will produce depends mostly on the size and material of the quantum dot. The reason for this is something called quantum confinement. The effect is similar to that of two different sized bells. When the larger one is struck, the result will be low energy sound waves, while the smaller one creates higher energy waves. When light excites a quantum dot, the larger the size of the dot, the lower the energy waves will be, resulting in a redder light. The smaller it is, the bluer the light will be. Quantum dots are currently used in biological and medical research, as well as in solar panels, televisions, and solid state lighting.