This book provides comprehensive insights into the latest basic and clinical developments in the field. The first part reviews recent findings and new technologies pertaining to basics of Jak-Stat function. The second part describes the evolution of Jak-Stat signaling and the role of the pathway in invertebrate organisms. The third part focuses on Jak-Stat signaling in hematopoietic cells under both physiological and pathophysiological conditions. Finally, chapters in the fourth section describe the relationship of Jak-Stat signaling to various states of disease, particularly infection, leukemias and solid cancers. The book is intended for all scientists in molecular biology, biochemistry and cell biology dealing with biomedical issues.