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Figure 1: The adult mammalian stem cell niche is defined as a microenvironment that facilitates (a) the survival and (b) the self-renewing capacity of the stem cells, as well as (c) the production of actively dividing precursors leading to the generation of a differentiated progeny. The stem cells retain their function as long as they remain anchored to the supporting cells and their divisions occur in such a way that one daughter cell keeps its contact with the supporting cell while the other one loses this contact, migrates from the niche, and (d) proceeds to generate terminally differentiated cells.