This book is the first scholarly history of research into the genetics of body cells, from its origins in the 19th century to the present day. Henry Harris, a well-known writer and a distinguished investigator in cell biology and cancer genetics, brings an unusually informed perspective to the technical aspects of his subject. He has written a book to be enjoyed not just by professional historians of science, but by working scientists in genetics, cell biology, and cancer research, from the graduate student level upwards. Its readers will derive a richer understanding of how and why the cells of the body are studied in the way that they are today.