Mosses have colonised almost every corner of the earth's surface. Evolving from oceanic algae that emerged onto the land 450 million years ago, these very first terrestrial plants became one of the main sources of oxygen for our evolving planet, helping to transform it from an arid rock into a lush world. This documentary travels to some of the most beautiful moss-covered landscapes in the world, including Japan, Iceland, France and Denmark, to meet the experts investigating its astonishing properties and potential. Science is only beginning to understand the secrets and possibilities of these remarkable plants.