This volume collects research on language, cognition, and communication in multilingualism. Apart from theoretical concerns including grammatical description, language-specific analyses, and modeling of multilingualism, different fields of study and research interests center around three core themes: The Early Years (aspects of language acquisition and development, including vernaculars or minority languages, reading, writing, and cognition, and multilingual extensions), Issues in Everyday Life (the role of multilingualism in and for speech–language–communication difficulties, including diagnosis, provisions of services, and later language breakdown), and From the Past to the Future (aspects of multilingualism beyond acquisition, education, or pathology, with a focus on heritage languages and translanguaging). Specialists from each of these areas introduce state-of-the-art research, novel experimental studies, and/or quantitative as well as qualitative data bearing on ‘multifaceted multilingualism’. There is a broad spectrum for take-home messages, ranging from new theoretical analyses or approaches to assess multilingual speakers all the way to recommendations for policy-makers.