Heart is a fancy electric pump!
The heart is indeed a biological miracle. Fist-sized, it pumps blood through the entire body for a whole life time, day and night. It is the blood which supplies nutrients and oxygen to the body. It is through the blood again , that waste products and carbon-dioxide are removed from it. Ironically, we hardly notice the good work of our heart, until it is sick. And when it is sick it could be too late.