MAPK, or Mitogen-Activated Protein Kinase, is a crucial signaling molecule in cells that helps transmit information from the cell surface to the nucleus. It plays a vital role in various cellular processes, including growth, differentiation, and response to stress. MAPK pathways are activated by various stimuli, such as growth factors and cytokines, leading to a cascade of phosphorylation events that ultimately influence gene expression. There are several types of MAPK pathways, including ERK, JNK, and p38 MAPK, each with distinct functions and regulatory mechanisms. These pathways are essential for maintaining cellular homeostasis and are involved in numerous physiological processes, making them important targets for research in areas like cancer and inflammation.