The theoretical proposals brought forward in this book as well as the results from the reported experimental studies present genuine contributions to the biolinguistic program. The papers contribute to our understanding of the properties of the computations and the representations derived by the language faculty, viewed as an human biological organism. This volume adds to the usual notion of interfaces, which is generally understood as the connection between syntax and the semantic system, between phonology and the sensorimotor system. It raises novel interface questions about how these connections are at all possible within the biolinguistic program. It anchors the formal properties of grammar at the interfaces between language and biology, language and experience, bringing about language acquisition and language variation, and it also explores the interaction of grammar with the factors reducing complexity. This book aims to bring about further understanding of the interfaces of the grammar in a broader biolinguistic sense.