The deep terrestrial subsurface environment is distinct from the shallow subsurface due to significantly longer groundwater residence times and represents regional rather than local precipitation-responsive hydrology. The presence of a large, deep subsurface biomass (approximately 25% of the earth’s microbial biomass) has fundamental scientific implications as well as practical impact on large-scale engineering projects (e.g. underground constructions). Nutrient and energy transformation pathways in the Earth’s subsurface are poorly understood and it is not well known how such oligotrophic environments can support life in the terrestrial deep biosphere. The deep subsurface is also important as a potential reservoir for microbes that evolved with evolutionary pressures distinct from those at the surface and may also be relevant for constraining putative life on other planets. We have performed a thorough taxonomic and functional profiling of the deep biosphere through the analysis of metagenomic and metatranscriptomic samples from different depths of several sites located in Sweden and Finland. Sequencing of single amplified genomes (SAGs) from the same sites has also been carried out in collaboration with the Joint Genome Institute (JGI). We have recently published this data set as the Fennoscandian Shield Genomic Database (FSGD) in the journal Nature Communications. We will now exploit the FSGD to further investigate the terrestrial deep biosphere communities such as community structure, how they survive, and their evolutionary pressures.