Fertilizer–without it two thirds of the world would starve. It makes our lawns grow greener and our crops grow taller. Take a tour of the places where the essential nutrients that feed the soil are harnessed. Dig deep in a phosphate mine, sniff around a sewage treatment plant and get dirty in a trough teeming with seven million worms. Finally, learn about a war that was fought over the control of bat poop!