The images, sensations and emotions we experience during sleep were once seen as the gateway to the gods and had the power to alter lives and even whole societies. Rajan Datar explores the way dreams, and their interpretation, have shaped beliefs and actions for thousands of years – from their role as a connection to the dead and the spirit world, to their ability to predict the future. We hear how these seemingly involuntary visions inspired key historical figures, changed the course of major events, and were used by many rulers as a propaganda tool. Plus, we discuss what’s really happening in our brains when we have dreams and ask whether 21st-century life is placing them under threat. Contributors: Sidarta Ribeiro, professor of neuroscience and founder of the Brain Institute at the Federal University of Rio Grande do Norte, in Brazil, and also the author of ‘The Oracle of Night: The History and Science of Dreams’; Scott Noegel, professor of biblical and ancient near eastern languages and literatures at the University of Washington, in the United States; Özgen Felek, lector of Ottoman and modern Turkish in the department of near eastern languages and civilizations at Yale University, in the US. Producer: Simon Tulett (Picture: Dreamlike scene of a woman standing at fork in a stone pathway in a calm lake with clouds reflecting in the water. Credit: Thomas Barwick/Getty Images)