This paper investigates developmental changes, as well as inter-linguistic and inter-individual variations, in the expansion and composition of French children's early lexicons. Two studies were conducted using children's naturalistic productions: a longitudinal study of one child between 1;2 and 2;6, and a cross-sectional study of two groups (12 children each) aged 1;8 and 2;6. Analyses indicate that lexical productivity (measured in types, tokens, and new words) strongly increased with age, whereas lexical diversity showed almost no developmental progression. Nouns and para-lexical elements (including interjections, fillers or formulas) were predominant until 1;8 and decreased over time, while predicates and grammatical words increased. As compared to English, French development was characterized by less frequent nouns, initially more frequent predicates, and a remarkable expansion of grammatical words. Inter-individual variability in lexical productivity, in lexical diversity, and in the proportions of different categories was more marked at 1;8 than at 2;6. Lexical profiles found at 1;8 suggest the existence of more diversified organizational patterns than those captured in the referential-expressive distinction.