In this episode of "THE BODY," we focus on a pair of small, often-overlooked organs: the kidneys. When people think of the kidneys, one thing probably comes to mind - the role they play in producing urine. But they are key nodes in a vast, internal network of organs that constantly communicate with one another. And some of the messages the kidneys transmit help control blood pressure and maintain the body's supply of oxygen. They have a significant influence on human health. We use cutting-edge imaging technology to explore the power of the kidneys to determine how well – and how long – we live.