A mood ring is a ring that contains a thermochromic element, such as liquid crystals. The ring changes color in response to the body temperature of the wearer. The color is used, by some proponents, to show the emotional state of the carrier. The mood ring was coined in 1975 by two New York inventors, Josh Reynolds and Maris Ambats who combined bound liquid crystals with quartz stones in rings. They sold them initially retail for $ 45 for a "silver ring" and $ 250 for gold, they increasingly became a rage in the 70s A mood ring is a specialized liquid crystal thermometer, portable on the finger. The ring is usually decorated with a faux gemstone (usually made of quartz or glass) that is either a clear capsule filled with thermochromic liquid crystals, or has a thin sheet of liquid crystals sealed under. Changes in temperature cause crystal different wavelengths of light that the color of the stone changes. The liquid crystal which is usually set up in the mood rings to a "neutral" color on the average human skin temperature, which is about 37 ° C. to give The theory behind the idea that the ring, the mood of the wearer is indicated based on a claim that body heat fluctuates with the emotional state of the carrier. Human body temperature is known to differ by small amounts (less than 0.5 ° C) over the circadian and menstrual cycles, and when the body fights an infection. Variations in the air temperature seem to be a greater effect on the temperature of the ring than to have changes in the body temperature of the wearer. No direct correspondence between a mood and an individual color is ever substantiated.