This monograph is dedicated to the lives and scientific achievements of the physiology pioneers Warren and Margaret Lewis. Their story spans the first half of the 20^th century, from their respective educations through early, independent research to joint research from 1910 to 1955. Among the numerous developments they initiated, were the discovery of pinocytosis, the beginnings of video microscopy and the development of the first mammalian tissue cultures. Their research expanded the theoretical knowledge of cell structure and function. On a more practical level,...