Aging theories seek to explain the biological and psychological processes that contribute to aging. Two main categories are the programmed theories, which suggest that aging follows a biological timetable, and the damage theories, which propose that aging results from accumulated damage to cells and tissues over time. Among the programmed theories, the telomere theory highlights how the shortening of telomeres, protective caps on chromosomes, limits cell division. In contrast, the free radical theory within damage theories posits that reactive molecules can cause cellular damage, leading to the aging process and age-related diseases.