The capacity of the cells to send, process and accept signals with its environment and with itself is termed as cell signaling. Cells of every living organism exhibit this property. Some of the major types of cell signals are autocrine, juxtacrine, endocrine, intracrine and paracrine. The chemical signals or physical stimuli are detected by protein which is present within the cell or on its surface. These proteins are known as receptors. The cells are programmed to respond to particular extracellular signal molecules. Anomalies in cell signaling can lead to diseases such as cancer, diabetes and autoimmunity. This book unfolds the innovative aspects of cell signaling which will be crucial for the progress of this field in the future. Such selected concepts that redefine the research within this field have been presented herein. This book will serve as a valuable source of reference for graduate and post graduate students.