The MAPK pathway, or Mitogen-Activated Protein Kinase pathway, is a crucial signaling cascade in cells that helps regulate various cellular processes, including growth, differentiation, and response to stress. It involves a series of protein kinases that activate each other in a specific sequence, ultimately leading to the activation of transcription factors that influence gene expression. This pathway is often triggered by external signals, such as growth factors or cytokines, binding to cell surface receptors. Once activated, the MAPK pathway can affect numerous cellular functions, making it essential for normal development and functioning, as well as for understanding diseases like cancer, where this pathway may become dysregulated.