The TGF-β signaling pathway is a crucial cellular communication system that regulates various biological processes, including cell growth, differentiation, and immune responses. It is activated by transforming growth factor-beta (TGF-β), a cytokine that binds to specific receptors on the cell surface, initiating a cascade of intracellular signaling events. Once activated, the pathway primarily involves the phosphorylation of SMAD proteins, which translocate to the nucleus to influence gene expression. This signaling pathway plays a significant role in tissue development, repair, and the regulation of inflammation, making it important in both normal physiology and disease states, such as cancer and fibrosis.