In biology, cell signaling (cell signalling in British English), or cell-cell communication, governs the basic activities of cells and coordinates multiple-cell actions. A signal is an entity that codes or conveys information. Biological processes are complex molecular interactions that involve many signals. The ability of cells to perceive and correctly respond to their microenvironment is the basis of development, tissue repair, and immunity, as well as normal tissue homeostasis. Errors in signaling interactions and cellular information processing may cause diseases such as cancer, autoimmunity, and diabetes. By understanding cell signaling, clinicians may treat diseases more effectively and, theoretically, researchers may develop artificial tissues.