What are the manifestations of solar activity? Two scientists (Nicole Vilmer, from the Observatory of Paris, France, and Laure Lefèvre, from the Royal Observatory of Belgium) discuss this topic. This movie was produced by COST action TOSCA (Towards a more complete assessment of the impact of solar variability on climate), a multidisciplinary European network of scientists from 20 countries whose objective is to provide a better understanding of the hotly debated role of the Sun in climate change. For more information, and more movies, see www.tosca-cost.eu