Microbial diversity in extreme habitats, e.g. the deep subsurface, polar regions, salt lakes, hot springs, solfataric field and alklaine lakes, is very broad and delivers a valuable resource of unique enzymes (extremozymes) and chemical compounds. The study of these extremophiles will provide new keys to the understanding of life processes under stress conditions and will unravel the mechanisms developed by biological systems to cope to harsh conditions. This gained knowledge will be used to develop new biobased products and bioprocesses in various fields such as fine chemicals, feed, food, cosmetics, textile, paper and pharmaceutical industries.