Senescent cells can display reinforcement, establishment, and change in their function and identity. (A) Differentiated senescent cells can display a reinforced identity and function: senescent β cells secrete more insulin; senescent T cells produce more IFNγ, TNFα, and granzymes; senescent macrophages display increased phagocytic activity. (B) Entry into senescence can contribute to establishing cell identity and cell function as shown here for maturation of syncytiotrophoblasts and production of mature megakaryocytes. (C) Senescence can change cell function and identity: adipocytes can change their properties depending on whether they are senescing or not, and epithelial cells can display transdifferentiation when they are senescing (EMT has been reported in epithelial non-tumoral cells and NED reported in epithelial hormone-dependent cancer cells).