The Symphony Inside Your Chest

Every second of every day, your heart generates enough electrical activity to power a small lightbulb. Cardiologists at the Cleveland Clinic have mapped this system and found something remarkable: the sinoatrial node, a cluster of cells no bigger than a pencil eraser, fires between sixty and a hundred times per minute without a single conscious thought from you. It has been doing this since roughly twenty-two days after your conception — before your mother even knew you existed.…