The coordination of life in multicellular organisms is precisely controlled by cells via various internal and external signals. Cells depend on different types of signals to regulate their growth, division, metabolism as well as death. Signals are growth factors or hormones produced and secreted by other cells. Some signals such as nutrients are in the form of molecules from the environment. Signaling molecules are sensed by direct binding to specific receptor molecules. Depending on the biochemical properties and ways of molecules changes, we can group various signaling events in defined pathways. Throughout specific signal transduction pathways, a signal can modulate cellular activities and gene expression, thereby leading to changes in cell growth, metabolism, differentiation, or many other cellular functions. When genetic mutations or biochemical changes occur in key proteins of certain cellular signaling pathways, cellular homeostasis can be disrupted, thus triggering tissue malfunctions, itiation or spread of cancer, or developmental anomalies. Dissecting biochemical principles of these cell signaling pathways is essential for us to better understand mechanisms of both normal cells and pathological conditions, therefore our knowledge on signal transduction will provide valuable information to develop effective therapeutic agents to fight against diseases.. This 6 week-course will give you a solid introduction to the basic fundamentals of cell signaling. I will first define the concept of cell signaling and introduces major types of cellular signaling events. Throughout 6 weeks, we will study biochemical basis of electrical signaling, chemical signaling as well as gap junction-mediated signaling pathways. We will also learn about key principles underlying signal transduction pathways by studying significance of protein-protein interactions and signaling second messengers. In the end of each week, dysregulated cell signaling in pathological conditions such as cancer and diabetes will be presented and discussed. Everyone knows that cell signaling is essential for sustaining life. How can you explain insulin actions in lowering glucose in biochemical details? What can be the fundamental mode of oxygen sensing in our body? Have you ever thought about ways of how we can specifically remove or kill certain types of rapidly-growing cancer cells? Cell signaling accompanies various biochemical strategies to sense and transmit signals inside our cells. Without fine control of those signaling processes, cells, tissues, and organisms cannot maintain life.