What are the functions of cell signaling?

Cell signaling is an essential, ubiquitous process by which cells communicate with each other and the environment, enabling them to work together and react to changes in their surroundings. 

Cell signaling regulates vital cellular activities such as gene expression, metabolism, cell division, differentiation, movement, and programmed cell death. 

Cell-to-cell signaling coordinates the activities of individual cells allowing multicellular organisms to function more efficiently.