Consider how you​—some 100 trillion cells of you—​came about. You began as a single cell that was formed when the sperm from your father united with an egg cell from your mother. At that uniting, the plans were drawn up within the DNA (short for deoxyribonucleic acid) of that newly formed cell to produce what eventually became you​—an entirely new and unique human. The instructions within the DNA “if written out,” it is said, “would fill a thousand 600-​page books.”

In time, that original cell began dividing, making two cells, then four, eight, and so on. Finally, after about 270 days​—during which time thousands of millions of cells of many different kinds had developed within your mother to form a baby—​YOU were born. It is as if that first cell had a huge room full of books with detailed instructions on how to make you. But just as wonderful is the fact that these complicated instructions were passed along to every succeeding cell. Yes, amazingly, each of the cells in your body has all the same information as the original fertilized egg contained!

Consider this also. Since each cell has the information to produce all kinds of cells, when it came time, say, to make heart cells, how were the instructions to make all the other cells suppressed? Seemingly, acting like a contractor with a complete cabinet of blueprints for making a baby, a cell picked from its file cabinet a blueprint for making heart cells. Another cell picked out a different blueprint with instructions for producing nerve cells, yet another took a blueprint for making liver cells, and so on. Surely, this still unexplained ability of a cell to select the instructions needed to produce a particular kind of cell and at the same time suppress all other instructions is another of the many “miracles that take us from conception to birth.”

The Brain

An even greater wonder is the development of the brain​—the most mysterious part of the human miracle. Three weeks after conception, brain cells start forming. In time, about 100 billion nerve cells, called neurons​—as many as there are stars in the Milky Way—​are packed into a human brain.