Unlike the previous chapters, in which an effort has been made to avoid technical terminology and many references to the work of others, this chapter gives the interested reader some information about the research that has informed this book. The chapter introduces some research into the advantages and possible disadvantages of bilingualism and delves into how children actually acquire more than one language. The basis for insisting on sufficient input in the minority languages is presented, along with work into differences between the language acquisition of children learning one or more than one language. The interrelated topics of how multilingual speakers use and combine their languages, how one language can be stronger than others and the effect of languages on each other are presented together.