This week we're diving deep into the history and current state of some of the largest and longest running studies in the world. We speak with science journalist, Chief Magazine Editor for Nature, and author Helen Pearson about her book "The Life Project: The Extraordinary Story of 70,000 Ordinary Lives" and the history of the long-running series of British longitudinal cohort studies. And we'll talk with Professor Parminder Raina about the Canadian Longitudinal Study on Aging an what it's like to be at the beginning of a cohort study that could run for decades.