Since Juan Uriagereka originated the multiple spell-out model in 1999 it has been one of the most influential lines of research in syntactic theorizing. The model simplified a crucial element of the minimalist account of language making it a more accurate reflection of syntax and its acquisition. In this book he explores important consequences of the multiple spell-out hypothesis and of the linked notion of cyclicity. He combines the latest thinking in linguistics with perspectives drawn from physics, biology, and animal behavior, aiming thereby to advance the field first described by Noam Chomsky as biolinguistics.