Local roads are one form of comunication. A city will rapidly grind to a halt unless there are effective communication systems between all the component parts, and particularly between the city and the rest of the world.
Cells depend crucially on communication and signalling. The
ability of a cell to interact with its neighbours - international communications - is as
important as local communication. Cells constantly exchange information in the form of chemical message or electrical signals. These signals are used, not simply to tell their neighbours where they are, but to help them grow and survive. The cells in our bodies are in touch with their nearest neighbours and with cells in distant parts. The brain in our head registers a toe twitching; our hand knows where to scratch an itchy back. There are elaborate systems for conveying these message between individual cells around the body.
