This occurs in superheating, supercooling, and supersaturation, for example. However, the drops themselves do not freeze, a phenomenon called supercooling (or forming "supercooled drops"). For instance, a glass is obtained by quenching (supercooling) a liquid. Supercooling is the cooling of a liquid below its freezing point without it becoming solid. Supercooling increases the medium viscosity but keeps the directional channels open for diffusion. Supercooling is often confused with freezing-point depression. One commercial application of supercooling is in refrigeration. Notice that formula 23 and formula 34 diminish with an increasing supercooling. Guth decided to solve this problem by suggesting a supercooling during a delayed phase transition. There are also "instant" slush drinks formed via supercooling. Although this supercooling phenomenon is poorly understood, it has been recognized through infrared thermography. Animals utilize supercooling to survive in extreme temperatures, as a last resort only. Frazil ice formation may also be started by snowfall, rather than supercooling. Supercooling is a last resort for animals. Even though supercooling is essential for survival, there are many risks associated with it.