Francisco Carrapiço is Professor at the Department of Plant Biology of the Faculty of Science of the University of Lisbon. He will take you to a journey down the microcosmos. Using Azolla as a case study, which is a water fern that lives on the surface of our Portuguese rivers and lakes, he will demonstrate how this fern forms a specific symbiotic association with Anabaena azollae, a bacterium that captures nitrogen from the atmosphere. To explain all this, he will use an optical microscope as well as your curiosity and imagination. Within this micro-ecosystem, these tools will take you where few have dared to go.