Cell signaling and signal transduction encompass the complex communication system that allows cells to perceive and respond to their microenvironment and to communicate with each other. This process begins when an extracellular signaling molecule, such as a hormone or growth factor, binds to a specific receptor on a target cell's surface or within its cytoplasm. This binding event triggers signal transduction, a cascade of intracellular molecular events that converts, amplifies, and relays the external signal to various effector proteins, ultimately culminating in a specific cellular response, such as a change in gene expression, metabolism, cell shape, or motility, which is fundamental for development, tissue repair, and homeostasis in multicellular organisms.