The human body is the most complicated machine in the world. We see with it, hear with it, breathe with it, walk and run with it, and sense pleasure with it. Its bones, muscles, arteries, veins and internal organs are organized with marvellous design, and when we examine this design in detail we find even more amazing facts. Every part of the body, though each may seem to be so different from another, is made up of the same material: cells.
Cells, each of which is one thousandth of a millimetre, are the structural units that form our body and everything in it. Some of these cells unite to form bones, others to form nerves, the liver, the inner layer of the stomach, the skin or the cornea of the eyeball. Each has the size and shape that exactly meet the requirement of that part of the body.
How and when did cells, which have such varied functions, come into being?
The answer to this question will take us into a process whose every moment is filled with mystery. All the approximately 100 trillion cells that make up your body today came from the division of one single cell. That single cell which had the same structure as all the cells in your body now, came from the union of your mother’s egg cell and your father’s sperm cell.