The ability of certain moss cultures to filter pollutants such as particulate matter and nitrogen oxides from the air makes them ideal natural air purifiers. But in cities, where air purification is a great challenge, mosses are barely able to survive due to their need for water and shade. This problem can be solved by connecting different mosses with fully automated water and nutrient provision based on unique Internet of Things technology. Air filtering performance is quantitatively proven and the plants’ requirements are measured in real time. That’s how the CityTree came into being – the world’s first bio-tech filter to quantifiably improve air quality.