The heart is a most incredible pump. About the size of a fist and weighing only about as much as one of your sneakers, in an average lifetime a heart will beat over two thousand million times without stopping for rest or repair. The heart pushes a stream of blood through sixty thousand miles of arteries, capillaries, and veins, a journey that carries nutrients and oxygen to every cell in your body. In stunning photographs that will amaze you with their beauty and color, you will also learn about bacteria-eating white blood cells, blood-clotting platelets, and the spongy marrow tissue, where every second three million red blood cells are made.
