The book is divided into two parts following an introductory chapter. The papers in Part I consider the first language acquisition of some complex structures such as different types of passives, relative clauses, questions and classes of predicates, with a look at children’s early sensitivity to seemingly complex domains, such as the Definiteness Effect and unaccusative predicates. Part II is dedicated to the acquisition of complex structures in different modes of acquisition. The papers here examine, sometimes comparatively, different conditions of language acquisition dealing with clitics, types of relative clauses or referential pronouns. The languages considered range from European Portuguese to Finnish, French, German, Italian and Romanian.