Extremophiles are organisms that are adapted to environments inhospitable for conventional life forms, e.g. extremes of salinity and temperature, oxygen-starved conditions, or exposure to toxic heavy metals and intense radiation. It turns out that one extremophile, Halobacterium sp. NRC-1, is resistant to all of the above extremes, and has become a favorite subject for in-depth post-genomic studies. This is because of our ability to easily culture it in the laboratory, knock out any of its non-essential genes, and simultaneously assay gene expression for all 2500 genes using DNA microarrays. The organism is a member of the Archaeal branch of the evolutionary tree, an evolutionary relic that displays some characteristics of higher organisms and exhibits novel features that make it ideal for applications in biotechnology.