Entering an Unseen World is an in-depth story about how a singular laboratory contributed to creating a new science, modern cell biology. The story begins in 1910, in a laboratory devoted to studying cancer at The Rockefeller Institute for Medical Research, and culminates in 1974 when the Nobel Prize was awarded to three pioneering scientists. Chapters devoted to the early years offer a compelling narrative about this laboratory while focusing on five aspects of how this science unfolded through time: the hundreds of scientists involved, a nurturing environment, the experimental procedures developed, the instruments devised and mastered, and the discoveries made in a previously unseen world. First-person chapters by more than 20 scientists associated with this laboratory follow. They describe their roles exploring the intricate and fascinating world inside living cells. Their stories show what it takes to create a science while revealing in detail what we now take for granted: the cell is the basic structural and functional unit of all known living organisms. Nearly 150 classic illustrations and photographs document the evolution of their discoveries. Entering an Unseen World conveys the excitement of process and progress as this science came to life.