Archaea reveal the amazing diversity of nature, surviving and thriving in environments that would kill the majority of organisms, including relatively high temperatures, often above 100°C, as found in geysers, black smokers, and oil wells. Others are found in very cold habitats or in highly-saline, acidic, or alkaline water. Despite this amazing diversity, and small size, they still share similarities with humans, including a common carbon-based biochemistry, a genetic code based on DNA, a cell-membrane, proteins and lipids, and so forth.
Another aspect they share with all living organisms is that they not only provide for their individual purpose (survival, maintenance, and multiplication), but also provide a larger purpose—serving in food chains, for example. Ecologically, methanogens play the vital role in anaerobic environments of removing excess hydrogen and fermentation products that have been produced by other forms of anaerobic respiration. Human creativity has even devised ways for them to serve directly human purposes. For example, the enzymes isolated from some extremophile archaea have proven to be of great use in the biotechnology industry, able to function under conditions that would denature enzymes taken from most "normal" organisms.