Accumulating evidence demonstrates that adult tissues contain a population of very pluripotent stem cells and recently our group identified a population of very small stem cells in murine bone marrow and other adult organs that express several markers characteristic for epiblast/germ line-derived cells. We named these rare cells "very small embryonic/epiblast like stem cells (VSELs)'. We hypothesized that these cells, which are deposited during early gastrulation in developing tissues/organs, play an important role in the turnover of tissue-specific/committed stem cells. Based on this, we envision that germ line is not only the origin but also a basis/skeleton for the stem cell compartment in adult life forms. We noticed that VSELs could be mobilized into peripheral blood and the number of these cells circulating in peripheral blood increases during stress and tissue/organ injuries (e.g., heart infarct, stroke). Furthermore, our data indicate that VSELs are protected from uncontrolled proliferation and teratoma formation by a unique pattern of methylation of selected somatic imprinted genes. Finally, we envision that, in pathological situations, VSELs could be involved in development of some malignan-cies (e.g., teratomas, germinal tumors, pediatric sarcomas).