Max Hentges (15) and Leopold Aschenbrenner (14) thought that the method currently used to measure particulate matter pollution in Berlin is inadequate. This is because there are only a few measuring points and the values are often only published after a delay. The low-cost monitoring, warning and forecasting system developed by the two students from Berlin, on the other hand, uses a comprehensive network of sensors to determine pollution levels in real time. Hentges and Aschenbrenner first constructed the prototype of such a sensor, which measures the light scattering from the microscopically small dust particles. They also built the necessary hardware and software for data transmission. Users can call up the current measured values and forecasts at any time via a smartphone app and receive warnings.