This book investigates how digital youth engage in computer-mediated communication (CMC) in the era of social media. Particularly focused on their uses of emoji, their motivations, attitudes and interpretations of emoji use, Emoji Speak provides the first book-level discussion looking at youth-to-youth Social Network Service (SNS) communication and emoji use. Where previous research on SNS communication has tended to focus on the English language, in this book Jieun Kiaer explores SNS as a global phenomenon. Presenting the results of empirical investigation through large-scale surveys, SNS corpora, and interviews with a wide pool of Chinese, Japanese, Korean, and British youth participants, Kiaer compares SNS communication across languages to provide insight in understanding youth language and their emojing behaviours. Arguing that the future of our modern languages lies within the multi-modal and multi-lingual linguistic behaviours found in SNS, Emoji Speak suggests that emoji use among young people is leading to the emergence of a new, 'social' grammar.