Fillers appear during the early grammaticalization process, roughly between the one- or two-word phase and the earliest grammar, in a variety of languages. Peters accurately points out there have been theoretical and methodological difficulties when trying to integrate the filler phenomenon in language acquisition theory, probably because fillers do not fit neatly into linguistic categories, nor a structure of ‘modules’. Her note is a major contribution to the solution of those problems. She gives us a rich review that can guide any reader – specialised or naive – to deep, critical insights and to the relevant research literature. In addition to this valuable contribution, she points the way to future work. The very richness makes it difficult to add any interesting comments. So these remarks will be limited to complementary concepts and data.