After embryonic development, the vast majority of cells are differentiated and all organs are
in place. Growth of the organism then ensues and continues until adulthood, whereupon cell
division largely ceases. In some tissues, notably the bone marrow, skin, and gut, cell
proliferation continues throughout life to replace cells lost by attrition. This regeneration is
fueled by rare, long-lived, and largely quiescent stem cells that give rise to committed
progenitors, which in turn generate large numbers of fully differentiated cells. Mounting …