In this chapter, we focus on the development of explanatory abilities in French children attending nursery and grade school. Even if young children are unable to produce written explanatory texts, there is nothing to stop them from formulating oral explanations. It is the "why" type explanation that we intend to examine here, and more specifically the way it develops with age. Furthermore, since speech acts are multimodal, children's explanatory verbal productions are frequently accompanied by bodily movements (hand and head gestures, facial expressions, changes of posture). The observation of gesture associated with speech provides data of considerable interest to anyone in the field of discourse development and the evolution of abstract thought. In the first section of this chapter, we start by defending the idea that the study of the way explanations develop is a valuable starting point in gaining an understanding of how children come to master the academic (i.e., monologic) uses of discourse. In section 2, we report certain data which shed light on the importance of gesture in spoken communication as well as other data which suggest that the gestural system associated with speech undergoes an undeniable development. In section 3, we document the methodological choices made for the study which underlie the results and analyses presented in this chapter. This comparative study consists of two facets, one relating to the explanatory behaviour of children aged 6 to 11 years and the other relating to the equivalent behaviour in younger children aged 3 to 6 years. In section 4, we present the most significant results of this study, showing that spoken explanations are more complex in older children than in younger ones. These results argue in favor of the idea that the ability to verbalize monologic explanations develops with age. The gestural aspects of children's explanations are discussed in sections 5, 6 and 7. First of all, it would appear to be gestures relating to abstract dimensions and discourse cohesion that are most prominent among the gestures that accompany the explanations produced by children aged 6 years and over (section 5). While the utilization of such gestures is well