Epigenetics is the science of living DNA, charting the chemical pathways that spur DNA into action by turning genes on and off. While the Human Genome Project of the early 2000s was hailed as the key to understanding human heredity and disease, that historic effort was just the beginning. It has taken epigenetics to fill in the picture, explaining how the fixed code of our genome is implemented in countless living processes.

The promise of America is that the country is based on an idea, one where everyone is created equal and equally free to chart their own course. From 13 newly independent states ratifying a national constitution to the heated debates in the halls of Congress today, American politics is about negotiation over what our country is—and where we are going.

Railways are one of the most important inventions in modern history. From the 1825 opening of the Stockton and Darlington Railway in England, trains revolutionized both travel and trade and radically changed the way we experience the world. In the 24 richly illustrated lectures of How Railways Transformed the World, you’ll experience the amazing world and impact of railways, from the early 19th century to today’s futuristic trains, including extensive material on the pleasure and appeal of rail travel today.

Fadel Zeidan, research director of the University of California, San Diego Center for Mindfulness, is an expert on the neural mechanisms that support mindfulness- and meditation-based pain relief. In his Audible Original, Mindfulness for Pain Relief, he shows you how mindfulness meditation—even for short periods of time—can bring your experience of pain under control.

“Who are you?” Chances are you’d answer this question by describing the highlights of your personality and life experiences. But if you’d been asked this same question yesterday, you might have responded with a slightly different description. Does that mean you are a particular person today but were a different person yesterday? And what about tomorrow? Welcome to the slippery, shape-shifting nature of memory. As Professor Gabrielle Principe reveals, “you” are the conglomeration of the often-unreliable information your brain decides to feed you at any given moment.