Thinking about fungi makes the world look different. Most fungi live out of sight, yet make up a massively diverse kingdom of organisms that support and sustain nearly all living systems. Fungi throw our concepts of individuality and even intelligence into question. They can change our minds, heal our bodies, and help remediate environmental disaster. In this discussion with the award-winning journalist Howie Kahn, Merlin discusses the ways these extraordinary organisms – and our relationships with them – change our understanding of the planet on which we live, and the ways that we think, feel, and behave.