Although collective emotions have a long tradition in scientific inquiry, for instance in mass psychology and the sociology of rituals and social movements, their importance for individuals and the social world has never been more obvious than in the past decades. The Arab Spring revolution, the Occupy Wall Street movement, and mass gatherings at music festivals or mega sports events clearly show the impact collective emotions have both in terms of driving conflict and in uniting people. But these examples only show the most obvious and evident forms of collective emotions. Others are more subtle, although less important: shared moods, emotional atmospheres, and intergroup emotions are part and parcel of our social life. Although these phenomena go hand in hand with any formation of sociality, they are little understood. Moreover, there still is a large gap in our understanding of individual emotions on the one hand and collective emotional phenomena on the other hand.