Laughter is pervasive in interaction yet often overlooked in the research. This volume presents a collection of original studies revealing the highly-ordered, complex, and important phenomenon of laughter in everyday interactions. Building on 40 years of conversation analytic research, the authors show how the design and placement of laughs contribute to unfolding sequences, social activities, identities, and relationships. In this revealing study leading experts investigate laughter in a range of different contexts and across a variety of languages. The research demonstrates that laughter is not simply a reaction to humour but is used in a fascinating array of different ways. Findings reported here include its use in clinics, employment interviews, news interviews, classrooms, the discourse of children with severe autism, and ordinary conversations. The acoustics of laughter and its relationship to movement, gaze and gesture are also explored. The volume brings together new and influential research into this phenomenon to present the state-of-the-art. It will be invaluable to anyone interested in the study of interaction, conversation analysis, humour and laughter.