This text presents the story of an ongoing, long-term study of a large group of Catholic nuns who have given Dr David Snowdon access to their medical and archival records and participate each year in comprehensive mental and physical examinations designed to measure the long-term effects of aging. They have also agreed to donate their brains upon death. So far there are 250 brains in the bank making it the world's largest of its kind. Dr Snowdon is one of the world's leading experts on Alzheimer's disease and director of the "Nun Study", a research project involving 678 Catholic sisters ranging in age from 75 to 104 and which has been running for the past 15 years. We get to know many of the nuns personally, and through them discover some of the ground-breaking work which the "Nun Study" has achieved.