Signal transduction comprises the intracellular biochemical signals which induce the appropriate cell response to an external stimulus. The players in signal transduction are diverse, from small molecules as first messengers, to proteins, receptors, transcription factors, among many others. The different signaling pathways and the crosstalk between them originates the unique signaling profile of every cell type in the human body. The cell signaling specificity depends on several aspects including protein composition, subcellular localization and complexes and gene promoters. This textbook provides a comprehensive overview of the specific signaling pathways on a variety of human tissues. This information can be of great value for health science researchers, professionals and students to understand key pathways for tissue-specific functions in the plethora of signals, signals receptors, transducers and effectors. Chapter 3 and 15 are available open access under a Creative Commons Attribution 4.0 International License via link.springer.com.