Signal Transducer and Activator of Transcription (STAT) is a family of proteins that play a crucial role in cellular signaling. They are activated by various cytokines and growth factors, which bind to their respective receptors on the cell surface. Once activated, STAT proteins translocate to the nucleus, where they regulate gene expression, influencing processes such as cell growth, differentiation, and immune responses. There are several members of the STAT family, including STAT1, STAT2, STAT3, and STAT5. Each member has specific functions and is activated by different signaling pathways. Dysregulation of STAT proteins is associated with various diseases, including cancer and autoimmune disorders.