The iSPEX-EU campaign is the first Europe-wide citizen-science photonics experiment to measure air pollution using smartphones from 1 September to 15 October 2015. With the iSPEX add-on and app, you can transform your smartphone into a scientific tool to measure tiny particles in the atmosphere that contribute to air pollution and its impacts in an as-yet poorly understood way. iSPEX-EU forms a network of thousands of people all over Europe that perform iSPEX measurements and provide information at locations and times that are not covered by current air pollution monitoring efforts – and we need your help! By joining iSPEX-EU you can be part of a major project to help understand our atmosphere and make an important scientific contribution!