102 ISSUE/PROBLEM (society issue, issue that is seen relevant from pupils’ perspective, issue linked to some nature phenomenon or phenomenon from pupils’ everyday life) In the video, postdoctoral researcher Otso Peräkylä talks about the circulation of water: evaporation, condensing first into clouds and then into rainwater. Recent climate research has revealed that tiny particles in the air are crucial in rain drops formation. What does that mean to climate change? INVESTIGATIONAL STAGE