The ERK pathway, also known as the MAPK/ERK pathway, is a crucial signaling pathway in cells that helps regulate various functions, including growth, differentiation, and survival. It is activated by external signals, such as growth factors, which bind to cell surface receptors. This activation triggers a cascade of events involving proteins that ultimately lead to the activation of ERK (extracellular signal-regulated kinase). Once activated, ERK moves into the cell nucleus, where it influences gene expression and cellular responses. The pathway plays a significant role in processes like cell division and development, making it important in both normal physiology and disease states, including cancer.