With classEx you can conduct interactive surveys and classroom experiments. Students log in with their mobile devices (smartphone or notebook) and can participate interactively at the lecture. Results are shown instantly on the presentation screen of the lecturer with concrete graphs. Knowledge questions and spontaneous tests can be integrated in lectures or presentations for all kinds of academic disciplines. It can be used in political sciences to simulate polls or elections, psychologists can test the effect of roles and scenarios and economists can access the strategic interaction in markets and the whole world of behavioral economics.