Touch is a very important form of communication. We touch somebody when we want to show love or sorrow, joy or approval. We touch babies and they smile. Research shows that babies who do not receive a loving touch usually develop abnormally. In the same manner, cells that do not receive the touch of other cells do not develop at all into specialized, functional cells. Why?
Remember we started as a single, fertilized cell? Well after fertilization, this single cell divided and divided until there were so many small cells that are literally clones – no different from each other. However, after they reached a certain number, they started communicating with each other through touch (through receptors on their membranes) and exchange of molecules. When the cells were dividing and dividing, there was not much communication going on. However, when they stopped dividing and started communicating with each other, something beautiful happened. The cells began to develop their own identities (in the language of developmental biology, this is called differentiation).
Some of the cells later started moving together until they reached a certain destination. There they establish their territory and develop into an intricately designed organ like the heart or the brain. Others formed the stomach or the lungs and all our other beautifully formed organs(in the language of developmental biology, again, this is called organogenesis).
It is amazing how a touch can change a clone-like cell to a beautiful beating heart cell or a fiery nerve cell.