Tissue resident stem cells (aka. adult stem cells) renew and repair our tissues. However, in order to secure tissue homeostasis, generation of new stem cells via self-renewal and their differentiation in to functional cells must be carefully balanced. During aging, multiple types of alterations directly in stem cells, or in their tissue neighbourhood can disturb this balance. Our laboratory studies both stem cell intrinsic, and extrinsic mechanisms altering tissue renewal capacity, and how such mechanisms ultimately result in the functional decline we recognize as aging.