Telomeres consist of repetitive DNA-protein complexes that cap the ends of vertebrate linear chromosomes. Their capping function and dynamics both with regard to structure and length are carefully orchestrated by many regulatory mechanisms and factors, with likely more yet to be described. Telomere shortening has been shown to be a major measurable molecular characteristic of aging of cells in vitro and in vivo and is thought to have evolved as a tumor protection mechanism in long-lived species. Regulators and modifiers of telomere dynamics and dynamics with age together with the consequences of telomere shortening and telomere dysfunction in the context of aging and aging-related disorders are discussed in this chapter.