Hyperthermophiles produce some of the bright colors of Grand Prismatic Spring, Yellowstone National Park
A hyperthermophile is an organism that thrives in extremely hot environments - that is, hotter than around 60°C. The optimal temperatures are between 80°C and 110°C; in fact, the recently-discovered "Strain 121"  has been able to double its population during 24 hours in an autoclave at 121°C (hence its name). Most hyperthermophiles are extremophile micro-organisms within the domain Archaea, although some bacteria and cyanobacteria are able to tolerate temperatures of around 70°C. Many hyperthermophiles are able to withstand other environmental extremes - for instance, high acidity or radiation levels.
Hyperthermophiles were first discovered in the 1960s in hot springs in Yellowstone National Park, Wyoming. Since then, more than fifty species have been discovered. The most hardy hyperthermophiles thus known live on the superheated walls of deep-sea hydrothermal vents, requiring temperatures of at least 90°C for survival.
Although no hyperthermophile has yet been discovered living at temperatures above 121°C, their existence is very possible (Strain 121 survived being heated to 130°C for 2 hours, but was not able to reproduce until it had been transferred into a fresh growth medium, at a relatively-cooler 103°C). However, it is thought unlikely that microbes could survive at 150°C or hotter, as the cohesion of DNA and other vital molecules begins to break down at this point.