Longevity is used, sometimes, as synonymous with life-span and represents the ability of an organism to live longer than expected. However, the meaning of longevity goes beyond and includes a series of methods, tools and theories to extend healthier life. To achieve this goal, many scientists have turned their attention to a particular group of people, centenarians, who show signs of extreme longevity allowing them to live longer and most of the time healthier. Centenarians are the best example of extreme longevity in our species, they represent a selected population in which the appearance of major age-related diseases, such as cancer, cardiovascular and metabolic diseases among others, have been consistently delayed or escaped.In this book different aspect of longevity will be discussed and topics on immunology, molecular biology, genetics, diet and age-related diseases analyzed. Articles in this book were originally published as a thematic series in the journal Immunity & Ageing Volume 9, April 2012.