Have you ever wondered why some 60-year-olds look and feel like 40-year-olds and why some 40-year-olds look and feel like 60-year-olds? Though many factors contribute to aging and illness, Dr. Elizabeth Blackburn — a Nobel laureate — and health psychologist Dr. Elissa Epel reveal the critical role that biological markers called telomerase and telomeres play in our health. Dr. Blackburn and Dr. Epel discuss how to increase not only your lifespan but your health-span (the number of years that you remain active and healthy). They say that to live healthier and younger, we need to understand how sleep, exercise, stress, and diet can affect our telomeres.