This research analyzes the first instances of metalinguistic utterances and its diverse functions, in children aged between 3 and 8 years, in adult/child and child/child natural conversational exchanges. First, we discuss the psychological conditions that, following different authors, human minds have to fulfil in order to utter sentences that can be qualified as metalinguistic. Our cross-aged research work has allowed us to establish a category system of children's metalanguage. Analyses of correlations between the latter and children's age and between categories, has enabled us to order categories in terms of their emergence. Thus, we have achieved an overview of the development of children's metalanguage, which is progress in a field as yet little explored.