Henry Harris here provides an account of how scientists came to understand that the bodies of all living things are composed of microscopic units thta we now call cells. Harris turns to the primary literature - the original texts, scientific papers, and correspondance of medical researchers involved in the formulation of the cell doctrine - to reconstruct the events that enabled researchers to comprehend the nature and purpose of cells. Translating many of these documents into English for the first time, Harris uncovers a version of events quite different from that described in conventional science textbooks. Focusing on the scientific history of the genesis of the cell doctrine, the author also considers contemporary social and political contexts and shows how these influenced what experiments were undertaken and how the results were represented. He describes the intellectual struggles of pioneers across Europe, including Czech, Polish, and Russian scientists whose contibutors have been largely overlooked, and explores their false starts, blind alleys, and detours as well as triumphant verifiable discoveries. The book includes a collection of photographs that portrays those involved in the scientific quest and their observations.