The significant progress in the clarification of cellular mechanisms governing tissue homeostasis and physiological remodeling was achieved in recent decades. Undifferentiated cells such as multipotent mesenchymal stromal (stem) cells (MMSCs) play an important role in these processes. MMSCs reside in virtually all postnatal organs and tissues occupying a specific tissue niche associated with the perivascular spaces. The most important property of MMSCs is, on the one hand, their ability to provide structural integrity of tissues and on the other - to respond on paracrine stimuli and migrate into the site of injury, promoting the tissue repair. The main feature of the MMSC physiological and regenerative milieu is a low oxygen tension, which can significantly modify the properties ofstromal cells. This review is concerned with analysis of the recent data on the MMSC tissue niches in terms of integration of these cells into the comprehensive physiological and reparative tissue remodeling and the role of the partial oxygen pressure in the realization of MMSCs.