The aim of the course is to introduce students to the study of a specific type of contact languages, namely the heritage languages. These are the language varieties spoken by second and third generations immigrants. The course will start by providing a description of heritage speakers and their acquisition process, the type of bilingualism, and the environmental conditions that influence their language development. In order to frame the phenomenon, some theoretical approaches explaining heritage language acquisition will be discussed together with the main sources of divergence between the heritage language and the baseline language (the language spoken by the first generation and/or in the homeland), such as dominant language transfer, incomplete acquisition, attrition, universal principles, and a qualitatively different input. After proposing some methodological considerations and research ideas, I will present numerous examples of contact phenomena, at the phonetic-phonological, morphological, syntactic, semantic, and pragmatic level. In the final part of the course, I will illustrate the case study of heritage speakers of Malay in the Netherlands. In the last three lectures students will be asked to present an article that they have been asked to read.